Етикет: информатика

Key Words: LibreOffice Calc; multi-objective optimization; NLP Solver.

Abstract. There is a common difference between single-objective optimization and multi-objective optimization. In the first case, there is only a single value as a result of the optimization. In the second case, there is a set of solutions called Pareto-optimal solutions. Single-objective solvers are giving only a single value as a result, even for multimodal functions. Because of this single-objective solver is not proper for multi-objective problems. Through additional adaptation, a single-objective solver is possible to start multiple times. Taking the results of multiple starts, the Pareto front is marked. When the solver is a metaheuristic, the front itself is difficult to achieve. With fine-tuning of the solver’s parameters, the solutions can be as close as possible.

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Key Words: Bragg fiber; bending; losses; Photonic Crystal Fiber; model of deformation.

Abstract. The article analyzes the losses in one type of Photonic Crystal Fiber – Bragg fiber. It is one-dimensional fiber, made as coaxial cylindrical layers. The fiber cladding is a dielectric mirror realized as a multilayer dielectric coating. The paper proposes a method based on geometric optics for the analysis of light propagation losses in a multilayer microstructured fiber with an air core, as a result of tunneling. A model of M-layer fiber with set refractive indices of the dielectric layers is proposed. The angles of incidence and reflection of the boundaries of each two layers of the fiber cladding according to Snelius’ law are calculated. The transverse reflection coefficients of each boundary between two layers for TM and TE polarization are calculated. The electric fields of the reflected and incident beams are calculated. The magnitudes of these vectors are recursively related to each boundary of the previous and next fiber layer. The input power of the light in the first fiber layer for TE and TM polarization is calculated. The losses from light reflection when it passing through all layers of the fiber as a function of the reflection coefficients are calculated. The normalized attenuation is calculated. The characteristic equation for the optical waveguide is decided. The angles of reflection in different modes are calculated. The distance between two consecutive reflections of the beam is calculated as a function of the reflection coefficients for the different polarizations and the reflection angles of the layers for TE and TM polarizations. They determine the reflection coefficient and the phase change when light passes through the whole fiber. The delays of the rays with TE and TM polarization are obtained. The expressions for the chromatic dispersion of the fiber for TE and TM polarization are then derived. A mathematical model of the deformation, presented as a change in the geometry of the fiber in this section as part of a circle is proposed. For this section of the deformed fiber by geometric transformations the connection between the angles of incidence and reflection in the straight and in the round section of the deformed fiber is calculated. The distance between two consecutive reflections from the fiber boundary surface of the rays trajectory is determined by the number of consecutive reflections in the core of the fiber. The reflection losses in TE and TM polarization, which are proportional to the number of beam reflections, are then determined. The phase delays for beams with TE and TM polarization for a fiber of a certain length are determined as the sum of the individual delays in the reflections of the beams. The proposed mathematical model and algorithm for calculating the attenuation of the fiber for different modes of TE and TM polarization, an example of M-layer PCF fiber with air core and alternating dielectric layers with two alternating coefficients and thicknesses is solved, so as to create at the average wavelength of light a phase shift of 900. A MATLAB program has been written. It simulates the attenuation and dispersion of a fiber with set optical parameters. After solving the characteristic equation for this fiber with the introduced parameters, the normalized attenuations for TE and TM polarization are calculated for fiber with and without deformation for different propagating modes. Calculations have been made for fibers with core radius of 20-200 μm for a light wavelength of 1559 nm. The attenuation and chromatic dispersion graphs for TE and TM polarization of several straight and deformed fibers with the same length and different number of layers were plotted. A conclusion about the influence of the core diameter, the bending radius and the number layers of the fiber cladding on the losses of the different propagated modes is made. A comparison of PCF losses and ordinary quartz single-mode fibers was made. In conclusion, the disadvantage of the proposed method is that only the meridional rays of the propagating light are analyzed and the dielectric losses in the fiber cladding are not taken into account. The advantage of the proposed method is the small computational complexity and the correct qualitative result of the PCF analysis with certain parameters. Guidelines for future development are proposed – analysis of the losses of the fiber, taking into account the non-meridional rays in the fiber. The possibilities for using PCF for information transmission and as dispersion compensators in telecommunications are pointed. The possibility of using the method for optimization of certain parameters of PCF of this kind is proposed.

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Key Words: Beacon deployment; indoor localization; Indoor Positioning Systems.

Abstract. Localization of visitors in public buildings is a key technology to create accessible environments using location-based services. The usability of these services and the satisfaction of their clients depend on the accurate calculation of the position of visitors. This is most often realized using wireless sensor networks. The localization accuracy depends on a number of factors, one of which is the deployment of the sensor nodes. This is a complex task, which is most often realized by experts. In this article, we offer a complete solution for creating systems for indoor localization, which includes: (1) Algorithm for fast partitioning of the building components into non-overlapping rectangles; (2) Algorithm for sensor nodes deployment based on the geometry of the rectangles obtained; and (3) Algorithm for optimizing the sensor nodes placement taking into account the connectivity between the building components (rooms and corridors), as well as the static objects, which are obstacles for radio signals. Numerous experiments have been implemented in stimulating and real environments, which prove the applicability of the proposed solution.

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Key Words: RAMI 4.0; IEC/EN 62264; asset; communication and presentation capabilities; activity; scheduling; model; web services; B2MML.

Abstract. The Reference Architectural Model for Industry (RAMI) 4.0 tends to unify the efforts for rapid development of new technologies of the information and communication technology sector by stating definitions of an asset and its role in the cyber-physical world with the use of presentation and communication functions applied to the asset. Furthermore, the standard describes how an asset should interact with the cyber-physical world. In order to introduce the asset as a conceptual fundament, the standard RAMI 4.0 extends the Equipment hierarchy model of another standard – IEC/EN 62264, which is well known and applied as an architectural framework within software integration projects of various information systems. The differences between, are that in IEC/EN 62264, a physical asset model corresponds to the equipment model, whereas the RAMI 4.0 states that an asset may present even a Product or Connected World (Cyber-Physical World). The introduced extension is necessary because th perspective of the two standards is different. IEC/EN 62264 defines objects and models for integration, in which a Product, as an abstraction of “what should be made?” is a part of Product Definition Model (Operations Definition Model), and when it is physically performed “what is actually made?”, it is a part of Material Model. As such, the objects “carrying” the integration information are different. The Connected world also is an asset in RAMI 4.0, because it has value for a company, while the whole subject of the IEC/EN 62264 standard is to integrate information systems, thus achieving “Connected World”. This is why the standard IEC/EN 62264 should be considered as a “roadmap” for the cyber-physical transformation of the RAMI 4.0 standard. The aim of the article is to discuss the importance and the assumption of non-implicit relations between the two standards as well as the concept for development of RAMI 4.0 administration shell based on IEC/EN 62264 architecture.

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Key Words: Artificial intelligence; intelligent learning system; integration; learning technologies; optimization; system of systems.

Abstract. The main problems related to the integration of diverse functional elements of advanced intelligent learning systems are considered. It is shown that the integration of the elements in the learning process is a complex multilayered process due to the great variety and complexity of the ongoing basic processes – cognitive, pedagogical, technological, social and interpersonal. It is emphasized that the need for the integration process to be solved as a multifactor optimization data-driven problem and the use of modern techniques in the field of artificial intelligence – machine learning, pattern recognition, natural language processes, network management.

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Key Words: Botnet attacks; DoS attacks; intrusion detecting system; genetic algorithms.

Abstract.  One of the most common attacks against information security is Botnet. Recognizing such attacks requires the development of effective security systems. Intrusion detection systems collect information from different sources in computer systems and networks. For most systems, this information is compared to predefined patterns of abuse to identify attacks and vulnerabilities. Much of the existing host-based systems for botnet detection use techniques based on anomalies or rules. This paper presents some aspects of the implementation of a host-based botnet attack detection system. The system uses an anomaly detection technique based on a genetic algorithm.

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Key Words: Ethereum; block chain; smart contract; crypto-token; crypto-currency.

Abstract.  The proposed paper realized a smart contract based on Ethereum blockchain. The decentralized crypto-token is created for Initial Coin Offering (ICO) and based on ERC20 standard. A web-based interface is created for sale of these crypto-tokens. The results from experimental tests are presented.

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Key Words: ModSecurity; HTTP; OWASP; Web Application; Firewall.

Abstract. The security of the information in the contemporary dynamic and information world is by priority importance. Every day the entire world alarms for different in their nature and object hacker’s attacks. The damages of those attacks are as well fiscal and moral. The most popular attacks against the web-applications are those with causing service denial (Denial of Service – DoS), the blocking of the functioning of different sites or entire systems. Protection opportunities of web-servers, functioning in real time of OWASP (Open Web Application Security Project) are presented in that material. The module ModSecurity provides a set of protection rules, based on control of the ingoing and outgoing traffic from the point of view of the server

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Key Words: Wireless LAN (WLAN) security; WEP; RC4; IEEE 802.11; IEEE 802.1X; IEEE 802.11i; WPA; TKIP; WPA2; AES; CCMP; KRACK attack.

Abstract. On the basis of extensive research in the specialized literature, a critical analysis of information security protocols in the standards for IEEE 802.11 wireless LAN (WLAN, WiFi) has been carried out. Finally, some conclusions and recommendations are made. The first WLAN security protocol – WEP is extremely insecure and should not be used. Due to the inherited vulnerabilities of WEP and the fact that some parts of TKIP (such as the Michael function) have some security deficiencies, WPA has already exhausted its role as a temporary WEP fix for legacy hardware and is not recommended. Despite the mathematically proven cryptographic security of the AES standard in CBC mode, a weakness in the cryptographic key management process makes it vulnerable and leads to a security breach of WPA2 in October 2017. Although the vulnerability is removable by patch, probably a lot of WiFi-Devices have not been updated, which puts users at risk. In addition, despite updates of the firmware and recommendations from information security professionals to circumvent and/or block the protocol breach, reports emerged in October 2018 that the vulnerability to KRACK was still being exploited.

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Поколението на седемте екрана – на телевизора, компютъра, лаптопа, таблета, фаблета, смартфона и интелигентния часовник не може и не бива да се обучава така, както са били обучавани неговите родители. Пред това поколение не може и не бива да се пише на черна дъска с бял тебешир. Замяната на черната дъска с бяла, а на тебешира – с маркер, не е дори и количествена промяна, т.е. това не е начинът да се привлече вниманието на днешните ученици и студенти и те да се мотивират да акумулират знания и да развиват умения за практическото им прилагане. Необходимо е чрез масово и ефективно използване на информационни и комуникационни технологии, базирани иновационни образователни технологии и дидактически модели, да се адаптира образователната система към дигиталното поколение, а чрез въвеждане на изследователския подход в образователния процес той да се преориентира от механично усвояване на факти към преоткриване на знанията и развиване на уменията.

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