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1
Content available REST API SAFETY ASSURANCE BY MEANS OF HMAC MECHANISM
100%
Nowakowski G.
|
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nr 3
358-369
EN
The HMAC mechanism that enables authentication REST services and assures their integrity, non-repudiation and confidentiality, has been presented in this article. A demonstration Restful API has been implemented using Slim Framework, in which several endpoints for login, test route available only for registered users and authenticated by means of HMAC mechanism, have been assigned. The solution proposed here suggests an alternative that is easy to implement compared to other well-known methods of authentication and authorization.
2
Content available Metody zwiększające wydajność i bezpieczeństwo aplikacji internetowych
51%
Machulski T. , Nowakowski G. , Skublewska-Paszkowska M.
Journal of Computer Sciences Institute
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2019
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tom Vol. 12
206--213
PL
Artykuł prezentuje metody zwiększające wydajność i bezpieczeństwo aplikacji internetowych oraz ocenia ich wartość i zasadność użycia. Każda z przedstawionych metod została zaimplementowana w aplikacji testowej. W pracy zostały przedstawione wyniki badań porównujących stan aplikacji przed i po implementacji danej metody. Na podstawie rezultatów badań sformułowano wnioski dotyczące wpływu metod wydajności i bezpieczeństwa na zachowanie aplikacji testowej.
EN
This article presents the methods of enhancing the performance and security of web applications. It also evaluates them and describes how to use them. The methods have been implemented in a test application. The article presents results of the research comparing state of the application before and after implementation of every listed method. Conclusions about impact of the methods of enhancing performance and security of web applications are based on the results of the research.
3
Content available remote The approach to applications integration for world data center interdisciplinary scientific investigations
51%
Nowakowski G. , Telenyk S. , Yefremov K. , Khmeliuk V.
Annals of Computer Science and Information Systems
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2019
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tom Vol. 18
539--545
EN
The approach to applications integration for World Data Center (WDC) interdisciplinary scientific investigations is developed in the article. The integration is based on mathematical logic and artificial intelligence. Key elements of the approach - a multilevel system architecture, formal logical system, implementation - are based on intelligent agents interaction. The formal logical system is proposed. The inference method and mechanism of solution tree recovery are elaborated. The implementation of application integration for interdisciplinary scientific research is based on a stack of modern protocols, enabling communication of business processes over the transport layer of the OSI model. Application integration is also based on coordinated models of business processes, for which an integrated set of business applications are designed and realized.
4
Content available Simple and flexible way to integrate heterogeneous information systems and their services into the world data system
51%
Nowakowski G. , Telenyk S. , Yefremov K. , Khmeliuk V.
Journal of Automation Mobile Robotics and Intelligent Systems
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2021
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tom Vol. 15, No. 4
76--90
EN
The approach to applications integration for World Data Center (WDC) interdisciplinary scientific investigations is developed in the article. The integration is based on mathematical logic and artificial intelligence. Key elements of the approach – a multilevel system architecture, formal logical system, implementation – are based on intelligent agents interaction. The formal logical system is proposed. The inference method and mechanism of solution tree recovery are elaborated. The implementation of application integration for interdisciplinary scientific research is based on a stack of modern protocols, enabling communication of business processes over the transport layer of the OSI model. Application integration is also based on coordinated models of business processes, for which an integrated set of business applications are designed and realized.
5
Content available An analysis of the influence of famous people’s posts on social networks on the cryptocurrency exchange rate
45%
Telenyk S. , Nowakowski G. , Gavrilenko O. , Miahkyi M. , Khalus O.
Bulletin of the Polish Academy of Sciences. Technical Sciences
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2024
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tom Vol. 72, nr 4
art. no. e150117
EN
In this work, the level of influence of the posts published by famous people on social networks on the formation of the cryptocurrency exchange rate is investigated. Celebrities who are familiar with the financial industry, especially with the cryptocurrency market, or are somehow connected to a certain cryptocurrency, such as Elon Musk with Dogecoin, are chosen as experts whose influence through social media posts on cryptocurrency rates is examined. This research is conducted based on statistical analysis. Real cryptocurrency exchange rate forecasts for the selected time period and predicted ones for the same period, obtained using three algorithms, are utilized as a dataset. This paper uses methods such as statistical hypotheses regarding the significance of Spearman’s rank correlation coefficient and Pearson’s correlation. It is confirmed that the posts by famous people on social networks significantly affect the exchange rates of cryptocurrencies.
6
Content available Highly efficient scheduling algorithms for identical parallel machines with sufficient conditions for optimality of the solutions
38%
Telenyk S. , Nowakowski G. , Pavlov O. , Misura O. , Melnikov O. , Khalus O.
Bulletin of the Polish Academy of Sciences. Technical Sciences
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2024
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tom Vol. 72, nr 1
art. no. e148939
EN
This paper aims to develop new highly efficient PSC-algorithms (algorithms that contain a polynomial-time sub-algorithm with sufficient conditions for the optimality of the solutions obtained) for several interrelated problems involving identical parallel machine scheduling. These problems share common basic theoretical positions and common principles of their solving. Two main intractable scheduling problems are considered: (“Minimization of the total tardiness of jobs on parallel machines with machine release times and a common due date” (TTPR) and “Minimising the total tardiness of parallel machines completion times with respect to the common due date with machine release times” (TTCR)) and an auxiliary one (“Minimising the difference between the maximal and the minimal completion times of the machines” (MDMM)). The latter is used to efficiently solve the first two ones. For the TTPR problem and its generalisation in the case when there are machines with release times that extend past the common due date (TTPRE problem), new theoretical properties are given, which were obtained on the basis of the previously published ones. Based on the new theoretical results and computational experiments the PSC-algorithm solving these two problems is modified (sub-algorithms A1, A2). Then the auxiliary problem MDMM is considered and Algorithm A0 is proposed for its solving. Based on the analysis of computational experiments, A0 is included in the PSC-algorithm for solving the problems TTPR, TTPRE as its polynomial component for constructing a schedule with zero tardiness of jobs if such a schedule exists (a new third sufficient condition of optimality). Next, the second intractable combinatorial optimization problem TTCR is considered, deducing its sufficient conditions of optimality, and it is shown that Algorithm A0 is also an efficient polynomial component of the PSC-algorithm solving the TTCR problem. Next, the case of a schedule structure is analysed (partially tardy), in which the functionals of the TTPR and TTCR problems become identical. This facilitates the use of Algorithm A1 for the TTPR problem in this case of the TTCR problem. For Algorithm A1, in addition to the possibility of obtaining a better solution, there exists a theoretically proven estimate of the deviation of the solution from the optimum. Thus, the second PSC-algorithm solving the TTCR problem finds an exact solution or an approximate solution with a strict upper bound for its deviation from the optimum. The practicability of solving the problems under consideration is substantiated.
7
Content available A review of the importance of synchrophasor technology, smart grid, and applications
32%
Baba M. , Nor N. B. M. , Sheikh A. , Nowakowski G. , Masood F. , Rehman M. , Irfan M. , Arefin A. A. , Kumar R. , Baba A. M.
Bulletin of the Polish Academy of Sciences. Technical Sciences
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2022
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tom Vol. 70, nr 6
art. no. e143826
EN
The electrical network is a man-made complex network that makes it difficult to monitor and control the power system with traditional monitoring devices. Traditional devices have some limitations in real-time synchronization monitoring which leads to unwanted behavior and causes new challenges in the operation and control of the power systems. A Phasor measurement unit (PMU) is an advanced metering device that provides an accurate real-time and synchronized measurement of the voltage and current waveforms of the buses in which the PMU devices are directly connected in the grid station. The device is connected to the busbars of the power grid in the electrical distribution and transmission systems and provides time-synchronized measurement with the help of the Global Positioning System (GPS). However, the implementation and maintenance cost of the device is not bearable for the electrical utilities. Therefore, in recent work, many optimization approaches have been developed to overcome optimal placement of PMU problems to reduce the overall cost by providing complete electrical network observability with a minimal number of PMUs. This research paper reviews the importance of PMU for the modern electrical power system, the architecture of PMU, the differences between PMU, micro-PMU, SCADA, and smart grid (SG) relation with PMU, the sinusoidal waveform, and its phasor representation, and finally a list of PMU applications. The applications of PMU are widely involved in the operation of power systems ranging from power system control and monitor, distribution grid control, load shedding control and analyses, and state estimation which shows the importance of PMU for the modern world.
8
Content available Robust estimation based nonlinear higher order sliding mode control strategies for PMSG-WECS
32%
Nazir A. , Khan S. A. , Khan M. A. , Alam Z. , Khan I. , Irfan M. , Rehman S. , Nowakowski G.
Bulletin of the Polish Academy of Sciences. Technical Sciences
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2023
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tom Vol. 71, nr 5
art. no. e147063
EN
The wind energy conversion systems (WECS) suffer from an intermittent nature of source (wind) and the resulting disparity between power generation and electricity demand. Thus, WECS are required to be operated at maximum power point (MPP). This research paper addresses a sophisticated MPP tracking (MPPT) strategy to ensure optimum (maximum) power out of the WECS despite environmental (wind) variations. This study considers a WECS (fixed pitch, 3KW, variable speed) coupled with a permanent magnet synchronous generator (PMSG) and proposes three sliding mode control (SMC) based MPPT schemes, a conventional first order SMC (FOSMC), an integral back-stepping-based SMC (IBSMC) and a super-twisting reachability-based SMC, for maximizing the power output. However, the efficacy of MPPT/control schemes rely on availability of system parameters especially, uncertain/nonlinear dynamics and aerodynamic terms, which are not commonly accessible in practice. As a remedy, an off-line artificial function-fitting neural network (ANN) based on Levenberg-Marquardt algorithm is employed to enhance the performance and robustness of MPPT/control scheme by effectively imitating the uncertain/nonlinear drift terms in the control input pathways. Furthermore, the speed and missing derivative of a generator shaft are determined using a high-gain observer (HGO). Finally, a comparison is made among the stated strategies subjected to stochastic and deterministic wind speed profiles. Extensive MATLAB/Simulink simulations assess the effectiveness of the suggested approaches.
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