Papers by Radoslava Kraleva
Electronics, Jan 17, 2023
This article is an open access article distributed under the terms and conditions of the Creative... more This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY
International Journal of Power Electronics and Drive Systems, Jun 1, 2023
This research focuses on an analysis of different algorithms for the graph vertex coloring proble... more This research focuses on an analysis of different algorithms for the graph vertex coloring problem. Some approaches to solving the problem are discussed. Moreover, some studies for the problem and several methods for its solution are analyzed as well. An exact algorithm (using the backtracking method) is presented. The complexity analysis of the algorithm is discussed. Determining the average execution time of the exact algorithm is consistent with the multitasking mode of the operating system. This algorithm generates optimal solutions for all studied graphs. In addition, two heuristic algorithms for solving the graph vertex coloring problem are used as well. The results show that the exact algorithm can be used to solve the graph vertex coloring problem for small graphs with 30-35 vertices. For half of the graphs, all three algorithms have found the optimal solutions. The suboptimal solutions generated by the approximate algorithms are identical in terms of the number of colors needed to color the corresponding graphs. The results show that the linear increase in the number of vertices and edges of the analyzed graphs causes a linear increase in the number of colors needed to color these graphs.
International Journal of Power Electronics and Drive Systems, Jun 1, 2023
This study focuses on two heuristic algorithms for the graph vertex coloring problem: the sequent... more This study focuses on two heuristic algorithms for the graph vertex coloring problem: the sequential (greedy) coloring algorithm (SCA) and the Welsh-Powell algorithm (WPA). The code of the algorithms is presented and discussed. The methodology and conditions of the experiments are presented. The execution time of the algorithms was calculated as the average of four different starts of the algorithms for all analyzed graphs, taking into consideration the multitasking mode of the operating system. In the graphs with less than 600 vertices, in 90% of cases, both algorithms generated the same solutions. In only 10% of cases, the WPA algorithm generates better solutions. However, in the graphs with more than 1,000 vertices, in 35% of cases, the WPA algorithm generates better solutions. The results show that the difference in the execution time of the algorithms for all graphs is acceptable, but the quality of the solutions generated by the WPA algorithm in more than 20% of cases is better compared to the SC algorithm. The results also show that the quality of the solutions is not related to the number of iterations performed by the algorithms.
International Journal of Engineering Pedagogy (iJEP)
This paper deals with an analysis of three algorithms for the graph vertex cover problem. Certain... more This paper deals with an analysis of three algorithms for the graph vertex cover problem. Certain methods for solving this problem are analyzed. In addition, different studies on the problem and some approaches to its solution are discussed as well. An exact algorithm (based on the backtracking approach) is presented. Calculating the average time for execution of this algorithm is consistent with the multitasking way of work of the operating system. For this purpose, four different starts of the algorithm are made and then the average time of all of them is calculated. The exact algorithm found the optimal solutions for all analyzed graphs. Besides this algorithm, two other heuristic algorithms for solving the problem are discussed. For this study, an interactive application is developed to visualize the performance of the three algorithms and display the obtained results. The results show that for small graphs with no more than 25 vertices the exact algorithm can be used to solve o...
Electronics 2023, 12(3), 485, 2023
This research focuses on a software application providing opportunities for the processing and an... more This research focuses on a software application providing opportunities for the processing and analysis of data generated by a saccade sensor with human eye movements. The main functional opportunities of the developed application are presented as well. According to the methodology of the experiments, three experiments were prepared. The first was related to visualization of the stimuli on a stimulation computer display that was integrated into the developed application as a separate module. The second experiment was related to an interactive visualization of the projection of the eye movement of the participants in the experiment onto the stimulation computer display. The third experiment was related to an analysis of aggregated data on the decision time and the number of correct responses given by the participants to visual tasks. The tests showed that the application can be used as a stimulation center to visualize the stimuli and to recreate the experimental sessions. The summary of the results led to the conclusion that the number of correct responses to the visual tasks depended both on the type of motion of the stimuli and on the size of displacement from the center of the aperture.
In this article are discussed some problems in developing software related to the management of i... more In this article are discussed some problems in developing software related to the management of information flows. We presented the basic stages in their development. We bold a methodology for conceptual modeling and design of information systems of this type. In order to demonstrate the effectiveness of the proposed model is an information system for administrative services of graduate students in the university.
On model architecture for a children's speech recognition interactive dialog system
arXiv: Human-Computer Interaction, May 25, 2016
ABSTRACT
Федеральное государственное казенное образовательное учреждение высшего образования «Московский университет Министерства внутренних дел Российской Федерации им. В. Я. Кикотя», 2020
El presente artículo describe evidencia empírica de la aplicación de la curva de Laffer. A su vez... more El presente artículo describe evidencia empírica de la aplicación de la curva de Laffer. A su vez, incluye el desarrollo de un modelo aplicado a Ecuador, el cual pese a las limitaciones que existen para definir la "U" invertida y todo lo que conlleva, puede ser utilizado como una herramienta de diagnóstico de la política tributaria aplicada por un gobierno y como un predictor de su aporte en temas laborales y productivos.
International Journal of Electrical and Computer Engineering (IJECE), 2022
This research focuses on the k-center problem and its applications. Different methods for solving... more This research focuses on the k-center problem and its applications. Different methods for solving this problem are analyzed. The implementations of an exact algorithm and of an approximate algorithm are presented. The source code and the computation complexity of these algorithms are presented and analyzed. The multitasking mode of the operating system is taken into account considering the execution time of the algorithms. The results show that the approximate algorithm finds solutions that are not worse than two times optimal. In some case these solutions are very close to the optimal solutions, but this is true only for graphs with a smaller number of nodes. As the number of nodes in the graph increases (respectively the number of edges increases), the approximate solutions deviate from the optimal ones, but remain acceptable. These results give reason to conclude that for graphs with a small number of nodes the approximate algorithm finds comparable solutions with those founds by...
International Journal of Electrical and Computer Engineering, 2021
Data modeling and data processing are important activities in any scientific research. This resea... more Data modeling and data processing are important activities in any scientific research. This research focuses on the modeling of data and processing of data generated by a saccadometer. The approach used is based on the relational data model, but the processing and storage of the data is done with client datasets. The experiments were performed with 26 randomly selected files from a total of 264 experimental sessions. The data from each experimental session was stored in three different formats, respectively text, binary and extensible markup language (XML) based. The results showed that the text format and the binary format were the most compact. Several actions related to data processing were analyzed. Based on the results obtained, it was found that the two fastest actions are respectively loading data from a binary file and storing data into a binary file. In contrast, the two slowest actions were storing the data in XML format and loading the data from a text file, respectively....
International Journal on Advanced Science, Engineering and Information Technology, 2021
This paper presents a study on the N-Queens Problem. Different approaches to its solution discuss... more This paper presents a study on the N-Queens Problem. Different approaches to its solution discussed in the scientific literature are analyzed. The implementation of an algorithm based on the backtracking method is also presented. The algorithm is optimized to find solutions in a specific subset of configurations among all possible ones. With this approach, the computational complexity of the algorithm is reduced from exponential to quadratic. In this way, the algorithm finds all possible solutions in a shorter time: fundamental and their symmetrical equivalents. The methodology for conducting the experiments is presented. The purpose of the study, the tasks to be performed, and the conditions for conducting the experiments are presented as well. In connection with the research, an application that implements the presented algorithm has been developed. This application generated all the results obtained in this study. The experimental results show that with a linear increase in the number of queens (equivalent to a quadratic increase in the number of fields on the board, the number of recursive calls made by the algorithm increases exponentially. Similarly, the number of possible solutions, as well as the execution time of the algorithm (in the different modes of the application-internal, interactive, and combined), also increases exponentially. However, the algorithm's execution time in the internal mode is significantly shorter than in the other two modes-interactive and combined. The future guidelines for the study are presented.
International Journal on Advanced Science, Engineering and Information Technology, 2017
Designing applications adapted to the capabilities of each user is an important part of modern so... more Designing applications adapted to the capabilities of each user is an important part of modern software engineering. Children with Autism spectrum disorder and/or intellectual disabilities are a special group of users where standard application design is not a good approach. Some of them have speech disorders, others have disorders of the musculoskeletal system and in their cognitive development. In the literature, these children are referred to as children with special educational needs. Only few researchers are involved in the development of various computer technologies, including mobile applications appropriate for these children. Some specialized mobile applications for these users can be found in the different mobile stores. However, most of these apps are rather expensive or with inappropriate user interfaces. Another disadvantage in all the apps is the lack of support in the Bulgarian language. It makes them unusable for the youngest users with special needs in Bulgaria. A conceptual model based on the investigation of some existing applications, the well-established theoretical practices, and on the opinion of children without disorders is proposed in this paper. An approach to designing and developing the interactive mobile application ChilDiBu for children with special needs, suitable for the Windows Phone mobile operating system, is presented. ChilDiBu is a picture-based app that combines graphic images, texts and audio files which can be used to learn the Bulgarian alphabet, the numbers up to 20, some basic colors and the daily activities that children perform. The application is focused on the development of the fine motor skills, observation and decision-making skills which is completed with a puzzle for arranging the two-digit numbers. At the end of the paper the app interface, the way it is used and its app architecture are shown.
Journal of Computing Science and Engineering, 2019
The last decade has seen a rapid growth in the use of mobile devices all over the world. With an ... more The last decade has seen a rapid growth in the use of mobile devices all over the world. With an increasing use of mobile devices, mobile applications are becoming more diverse and complex, demanding more computational resources. However, mobile devices are typically resource-limited (i.e., a slower-speed CPU, a smaller memory) due to a variety of reasons. Mobile users will be capable of running applications with heavy computation if they can offload some of their computations to other places, such as a desktop or server machines. However, mobile users are typically subject to dynamically changing network environments, particularly, due to user mobility. This makes it hard to choose good offloading decisions in mobile environments. In general, users' mobility can provide some hints for upcoming changes to network environments. Motivated by this, we propose a mobility model of each individual user taking advantage of the regularity of his/her mobility pattern, and develop an offloading decision-making technique based on the mobility model. We evaluate our technique through trace-based simulation with real log data traces from 14 Android users. Our evaluation results show that the proposed technique can help boost the performance of mobile devices in terms of response time and energy consumption, when users are highly mobile.
International Journal of Electrical and Computer Engineering (IJECE), 2020
The lifestyle of the new people generation, called in the scientific literature Generation Z, is ... more The lifestyle of the new people generation, called in the scientific literature Generation Z, is closely related to the Internet, computer and information technology. Therefore, people and children belonging to this group can be viewed in terms of software technology as specific users who have high requirements regarding the functions and interface of the software applications, connectivity to social networks and instant communication via the Internet. This influenced not only on the teaching and learning methods but also on the software applications used in the learning process. In recent years, new theoretical teaching methods have emerged, and the number of electronic learning systems increased. However, students lack motivation for the learning process. This requires developing new conceptual models of training and learning software, tailored to the skills and preferences of the end-users. The young students up to 12 years of age: from kindergartens to preschools and primary sch...
Visual Analysis of Actions Performed with Big Graphs
International Journal of Innovative Technology and Exploring Engineering, 2019
The basic concepts of using application development environments are presented in this paper. The... more The basic concepts of using application development environments are presented in this paper. The way of using the GraphAnalyser application and its basic functions is also presented. All results of the experiments conducted are generated with this application. According to the experimental methodology, they fall into two groups: the first one includes actions related to the vertices of a graph, and the second one includes actions related to the edges and the dynamic allocation of memory to store the structure of a graph. The results show that when the number of vertices in a graph increases linearly, the time to add and remove these vertices also increases linearly. When the number of graph vertices increases linearly, the number of added vertices per millisecond remains relatively constant. However, the number of vertices removed for one millisecond for graphs containing between 10 and 70 million vertices varies. Similarly, when the number of graph edges increases linearly, the nu...
International Journal of Online Engineering (iJOE), 2018
In this paper, the results of a comparative analysis between different approaches to experimental... more In this paper, the results of a comparative analysis between different approaches to experimental data storage and processing are presented. Several studies related to the problem and some methods for solving it have been discussed. Different types of databases, ways of using them and the areas of their application are analyzed. For the purposes of the study, a relational database for storing and analyzing a specific data from behavioral experiments was designed. The methodology and conditions for conducting the experiments are described. Three different indicators were analyzed, respectively: memory required to store the data, time to load the data from an external file into computer memory and iteration time across all records through one cycle. The obtained results show that for storing a large number of records (in the order of tens of millions of rows), either dynamic arrays (stored on external media in binary file format), or an approach based on a local or remote database man...
International Journal on Advanced Science, Engineering and Information Technology, 2018
Mobile apps can be used in various environments and at any time. People used them for learning, c... more Mobile apps can be used in various environments and at any time. People used them for learning, communications, and entertainment. Because of the ease use of mobile devices interface (like smartphone and tablet), then everyone, including the children with special needs, can have used them. In recent years, there has been an increase in the efforts of educational institutions and of scientists to support children in their daily life. Ongoing developments in communication and information technologies contribute to this process. The main goal of this study is to present the basic functional requirements for the mobile apps for children with special needs. The current state of the scientific research related to the design and development of mobile apps is discussed. This issue became very important in the last years because of an increase in the number of children with special needs on a worldwide scale is observed. And the same time the increase in the use of mobile technologies of them. The proposed model for the evaluation of potential utility provides for the classification of the mobile applications designed for children with special needs about their functionality features. This model is based on our studies of the state-of-art scientific works of many authors. Whit the model for the evaluation of potential utility, the 27 mobile applications for children with special needs, downloaded from the mobile application stores: Apple Store, Google Play and Store Windows Phone Apps, were classified and analyzed. The results showed that despite the variety of mobile applications, those that are suitable for children with special needs are too few. Most of the applications cover only half of the evaluation criteria, which means they have functionalities only for individual needs. Therefore, the proposed utility function metrics of the evaluation can be used as a basis for interface developing for mobile apps, appropriate for children with special needs.
International Journal of Interactive Mobile Technologies (iJIM), 2017
Modern mobile devices are becoming more and more popular in children’s lives. Therefore, the deve... more Modern mobile devices are becoming more and more popular in children’s lives. Therefore, the development of appropriate applications for them is of crucial importance. This article focuses precisely on the design of interfaces for mobile application with the participation of children. An overview of contemporary research related to Child-Computer Interaction (CCI) is made. The opinion of the children aged from 4 to 13 years on the possibilities and the features of the interface of mobile applications is investigated. The results obtained are summarized and analyzed. The prototype of a mobile application which corresponds to the preferences of the children under investigation is presented. Finally, the article specifies some future directions for research.
International Journal of Advanced Computer Research, 2016
In these approaches UCTP is represented as a graph coloring problem . A similar approach related ... more In these approaches UCTP is represented as a graph coloring problem . A similar approach related to local search method will be discussed in more details below.
Biomath Communications, 2016
The use of graphs is widely applied in modeling and solving problems in the field of computer sci... more The use of graphs is widely applied in modeling and solving problems in the field of computer science and bioinformatics.Therefore, it is essential to develop and improve algorithms reducing their computational complexity and increasing the precision of the solutions generated by them as well as the size of the input data.In this study two well-known algorithms for solving the problem for finding a minimum Hamiltonian cycle in weighted, undirected and complete graph (also known as Travelling Salesman Problem –- TSP) are analyzed.The first algorithm is based on the backtracking method and it always finds the optimal solution, while with the second one, the genetic algorithm (GA), finding the optimal solution is not always guaranteed.The aims of the study are to determine: (1)which of the algorithms can be used so that the resulting solution is optimal or near-optimal and the execution time be reasonable depending on the size of the input data; (2)the influence of GA paramete...
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Papers by Radoslava Kraleva
that should begin in early childhood. However, the traditional approaches to learning and to the
classical curricula cannot be always relied on for this purpose. This article considers some of the
existing traditional programming languages and the possibility of their use by children up to 8 years
of age.
Keywords: Mobile applications for preschool children, mobile learning.
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