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Acta polytechnica HungaricaVolume 16, Issue No. 3. (2019.)


  • Petru Cristian Vălean ,
    Norbert Kazamer ,
    Dragoș-Toader Pascal ,
    Roxana Muntean ,
    István Barányi ,
    Gabriela Mărginean ,
    Viorel-Aurel Șerban :

    Abstract: Active mechanical components that work in highly aggressive environments require protection against premature deterioration and, at the same time, it is necessary to ensure a long lifespan. In order to achieve these important features, a protective coating can be added. In this work, a NiCrBSi self-fluxing alloy powder was employed, as feedstock material. The coating was deposited by means of oxyacetylene flame spraying process, achieving a thickness of approximately 1000 μm and exhibiting a high degree of porosity and a weak mechanical adhesion to the substrate. To improve these characteristics, a remelting process using high frequency currents was applied. After the remelting process, the porosity decreased, from an initial value of approximately 15%, to a final value under 3%. Although the microhardness values did not change significantly, both wear-rate and corrosion behavior improvement, after the electromagnetic remelting, was observed.

    Keywords: NiCrBSi; self-fluxing alloy; flame spraying; inductive remelting process; pin-on-disk; microhardness; corrosion behavior

  • Mani Mehraei ,
    Benedek Nagy ,
    Nımet Ilke Akcay ,
    Şükrü Tüzmen :

    Abstract: Thalassemia syndromes are a diverse group of inherited genetic disorders. There are different types of thalassemia disorders, such as, β-thalassemia, which is also called Mediterranean anemia, that is an inherited disease that played a major role in the American thriller movie, "Dying of the light" starring Nicolas Cage (Dec. 2014). In this study, we focus on the beta-globin (β-globin) gene family related disorders. We seek potential amelioration strategies for β-thalassemia and sickle cell anemia via γ-globin gene induction. In this work, a simulation model is developed, utilizing a reaction systems methodology. These systems are finite and based on a discrete time scale and can be used to describe and analyze complex biological systems and biological phenomenon. In our model, simulations of normal and abnormal cases of fetal, to adult hemoglobin switching developmental stage are illustrated. Various types of known and potential treatment strategies for β-thalassemia and sickle cell anemia cases from the literature have been utilized to validate our model, used for identifying new potential treatments to be tested by molecular biologists, in the future studies. Moreover, we propose a novel potential simulation, as a therapeutic means, for β-thalassemia and sickle cell anemia, by identifying FOG1 as a potential target. Finally, our proposed model, based on a reaction systems methodology, shows that inhibition of FOG1 expression by using methods, such as, RNAi induces γ-globin gene expression and can compensate for the lack of beta-globin in patients suffering from β-globin gene related diseases, such as, β-thalassemia and sickle cell anemia.

    Keywords: bioinformatics; hemoglobin switching; beta-globin; beta-thalassemia; reaction systems; simulation; modeling biological systems

  • Jakub Oravec ,
    Ján Turán ,
    Ąuboą Ovseník ,
    Tomáą Huszaník :

    Abstract: This paper describes a modification of a chaotic logistic map which could be exploited in a field of image encryption. After a summary of basic image encryption methods and problems, the paper mentions properties of a modified version of the logistic map. It is shown that the proposed changes help to achieve greater robustness against phase space reconstruction attacks. The paper also describes the usage of a modified map in an image encryption algorithm. Other techniques applied in the proposed algorithm include key diffusion, ciphertext chaining or four step diffusion stage. Evaluation of properties of the proposed algorithm is done by means of commonly used techniques. The numerical results are then compared with values obtained by other published algorithms.

    Keywords: image encryption; logistic map; phase space reconstruction

  • Mioljub Jovanović ,
    Goran ©imić ,
    Milan Čabarkapa ,
    Dragan Ranđelović ,
    Vojkan Nikolić ,
    Slobodan Nedeljković ,
    Petar Čisar :

    Abstract: This paper presents SEFRA - a web-based framework for searching Web content written in Serbian. SEFRA is an easily customizable hybrid solution that can be a platform for new search applications and/or a service for already existing ones. The proposed architecture solves the problems of indexing, searching and displaying search results adjusted for Serbian. It unifies several web technologies and services into one product suitable for use in the Western Balkan’s countries for helping e-Government citizens' services and other public-sector services, private company administration, solving specific search problems for academic institutions and scientific literature publishers, etc. The proposed solution uses advanced Serbian language services accessible over the Web. It is also implementable for any other language where the target language morphology service exists. In other words, architecture is also customizable in this direction. It should be noted that the proposed architecture is optimized from both backend and web front-end perspective. The source code can be pulled from https://bitbucket.org/mjovanov/pretraga/. The one application of the proposed architecture is experimentally demonstrated through the search of crime law documents of Serbia. The experimental usage of this implementation shows that the problem of search relevance, is well-solved and easily customizable.

    Keywords: web-based architecture; Serbian language text search; software implementation; search results

  • Mahmoud Hamouda ,
    László Számel :

    Abstract: The switched reluctance motor (SRM) is a powerful candidate for many domestic and industrial applications. However, the double salient structure and discrete commutation process make it very difficult to acquire the analytical model of SRM. The performance optimization of SRM is achieved mainly based on the observation and analysis of its static magnetization characteristics. This paper presents multi-objective optimization of SRM’s control parameters for optimum motor operation over wide range of speeds. The optimization aims to achieve the maximum torque production with the lowest copper loss. A searching algorithm is developed to find the base values as they vary for each operating point. The objective-function is calculated using a dynamic/actual simulation model of SRM. For a highly trusted model of SRM, the static magnetization characteristics of tested 8/6 SRM are measured experimentally. Then, the measured data are used to build the model in a MATLAB/Simulink environment. The proposed control is implemented using an artificial neural network (ANN). A series of simulations and experimental results are obtained to show the feasibility of the proposed control.

    Keywords: switched reluctance motor (SRM); control parameters; optimization; artificial neural network; MATLAB/Simulink; experimental

  • Radmila Gerov ,
    Zoran Jovanović :
    Parameter Estimation Method for the Unstable Time Delay Process101-120en [986.11 kB - PDF]EPA-02461-00088-0060

    Abstract: The paper considers the evaluation of all the three parameters of the unstable first order process with time delay by using the process data received from the closed loop step response under proportional control. The new method of analysis of parameters identification is presented. One is required to read five parameters from the closed loop step response for the purpose of applying the method. For the selected proportional controller gain and the received process gain, the time constant and time delay of the unstable first-order plus time delay model is received by solving a characteristic system equation using the features of the Lambert W function. The suggested way of parameter estimation is simple and it yields better results than the well-documented methods in literature which the present method is compared with. Simulation results are given for linear system and a nonlinear bioreactor system.

    Keywords: Delay system; Model reduction; System identification; Parameters estimations; Unstable system; Nonlinear bioreactor

  • Viktor Taneski ,
    Marjan Heričko ,
    Boątjan Brumen :
    Systematic Overview of Password Security Problems143-165en [597.39 kB - PDF]EPA-02461-00088-0080

    Abstract: Alphanumeric passwords are the first line of defense in security for most information systems. Morris and Thompson identified passwords as a weak point in an Information System’s security, 35 years ago. Their findings showed that 86% of the passwords were too short, contained lowercase letters only, digits only, were easily found in dictionaries and/or easily compromised. The objective of this paper is to perform a systematic literature review in the area of passwords and passwords security, in order to determine whether alphanumeric passwords are still weak, short and simple. The results show that only 42 out of 63 relevant studies propose a solid solution to deal with the identified problems with alphanumeric passwords, but only 17 have statistically verified it. We find that only 3 studies have a representative sample, which may indicate that the results of the majority of the studies cannot be generalized. We conclude that users and their alphanumeric passwords are still the “weakest link” in the “security chain”. Careless security behavior, involving password reuse, writing down and sharing passwords, along with an erroneous knowledge concerning what constitutes a secure password, are the main problems related to the issue of password security.

    Keywords: authentication; password security; password security problems; systematic literature review

  • Zoltán Balogh ,
    Martin Magdin ,
    György Molnár :

    Abstract: Face recognition and motion detection are described in the context of the construction of a system of intelligent solutions, for use in the home, that can be used as a single free standing functional unit or as an element of a bigger system, connected to the Internet of Things. To create a complex system, a micro PC, Raspberry Pi 3, was used together with an application capable of recognizing faces and detecting motion. The outputs are saved into cloud storage, for further processing or archiving. The monitoring system, as designed, can be used autonomously; with the use of a battery and a solar panel, it is possible to place it anywhere. Furthermore, it could be used in various fields, such as health care, for the real-time monitoring of patients, or in the tracking of the spatial activity of people and/or animals. Thus, the system created, may be regarded as a part of the IoT.

    Keywords: Computer Vision; Raspberry Pi; Face detection; OpenCV; Motion detection

  • Dalibor Kekić ,
    Miloą Milenković ,
    Aleksandar Čudan :

    Abstract: This paper focuses on finding a model to optimize the provision for international emergency help, for emergencies caused by natural or man-made disasters. Nowadays, natural and man-made disasters occur more often than before, possibly, due to climate change, industrial activity, urbanization and migration of people. The national institutions for protection and rescue, in many cases, when the emergency situation is declared, cannot often cope and need help. The international organizations have recognized needs to develop mechanisms, which can be used to help affected countries. Examples are European mechanisms for civil protection and numerous guidelines from the United Nations Office for the Coordination of Humanitarian Affairs (OCHA). If the affected country cannot solve the problems and minimize risks for their citizens, material and cultural heritage, Governments send an official request to International Organizations, to obtain different kinds of international help as quickly as possible. However, the problems can appear with costs and other needed resources for providing international help, in terms of country’s distance which could provide help or duplication of resources that should be available. Currently, International Organizations do not have the documents, guidelines or software to be used for an emergency, when they have to make optimal decisions, concerning which country will provide help. This can be recognized as a main research gap, which is addressed by this paper. This paper uses operational research, to develop an adjusted transportation model, for optimizing the provision of international help in emergency situations. The main goal of this paper is to find useful solutions for those responsible for emergency management in making decisions for providing help to affected countries. Moreover, we aim to develop a model that will facilitate the appropriate disposition of human and material resources to an affected country in experiencing a disaster. The applied method involves an application of an adjusted transportation model for the case study, based on a real emergency situation during the May floods of 2014, in the Republic of Serbia. Having this in mind, the authors try to provide general results and a model, with a recommendation of how the model can be applied to any emergency situation in the world. The applicability is obvious for the activities of international organizations responsible for emergency management.

    Keywords: costs; model; disasters; emergency situations; international help

  • Árpád Beszédes :

    Abstract: Fault localization (narrowing down the cause of a failure to a small number of suspicious components of the system) is an important concern in many different engineering fields and there have been a large number of algorithmic solutions proposed to aid this activity. In this work, we performed a systematic analysis of related literature, not limiting the search to any specific engineering field, with the aim to find solutions in non-software areas that could be successfully adapted to software fault localization. We found out that few areas have significant literature, in this topic, that are good candidates for adaptation (computer networks, for instance), and that although some classes of methods are less suitable, there are useful ideas in almost all fields that could potentially be reused for software fault localization.

    Keywords: faults/defects/failures; fault localization; software fault localization; literature review; method assessment

  • Jolán Velencei ,
    Ágnes Szeghegyi ,
    Zoltán Baracskai ,
    Beatrix Bókayné Andráskó :
    Modeling the Intuitive Decision-Maker’s Mindset227-240en [879.09 kB - PDF]EPA-02461-00088-0120

    Abstract: Today, the term, Working Memory, is closely associated with intelligence. We propose that in addition to improving and speeding-up analysis, Artificial Intelligence (AI) can also be useful as a supplement to Working Memory. It is generally accepted that working memory plays a crucial role in cognition and models by computers, can help us understand the human mind. Building an artificial working memory can bring further benefits; for example, it can separate retrieval from reasoning and therefore, can acquire new concepts. The aim of this research is to solve the capacity shortage problem of Working Memory, by using AI as a supplement. In order to develop our argument, we characterize the ID3 algorithm as a way of looking for a consistent solution in the existing Case Based Graph; as the ID3 algorithm builds it from an empty graph, to an increasingly complex one. Methodologically, our study is based on observation of several Digital Natives (DNs) playing different games at Mobilis Interactive Exhibition Center in Győr, Hungary. The aim is to explore the behavior of the DN generation. By identifying the different mindset patterns of DNs, we will be able to observe how different DNs can be facilitated, to enjoy the games, rather than being bored, anxious or even, becoming addicted.

    Keywords: Artificial Intelligence; Knowledge-based System; Machine Learning