Browsing by Issue Date, starting with "2021"

Now showing 1 - 20 of 313

Access status: Open Access ,
Optimization of a gating system by means of simulation software to eliminate cold shut defects in casting
(AGH University of Science and Technology Press, 2021) Šabík, Vladimír; Futáš, Peter; Pribulová, Alena; Delimanová, Petra
The current trend in foundries is to achieve the production of high quality and competitive cast components. The innovation and optimization of current processes is a necessary element to achieve this goal. With the help of numerical simulations, it is possible to replace financially demanding and time-consuming experiments in real conditions with simulations that can reliably represent foundry process using computer technology. By a detailed analysis of the simulation results, we can predict various risks that could negatively affect the production process. This article monitors the influence of changes in the design of the gating system on the surface quality of a clutch wheel casting made of ductile iron, in the production of which two models of the gating system for casting were constructed in CAD software. Verification of gating systems was performed using the simulation software NovaFlow & Solid. The aim of the design change of the gating system is to reduce the amount of liquid metal used per casting, which can have a significant economic impact on industrial production. For this purpose, several simulations of the gating system of the casting were performed, while 2 which are the most representative for the mentioned problem were selected for the needs of the article. The main task of the simulation was to set the cellular network and conditions as close as possible to the reality of casting and the subsequent design and modification of the gating system.
Access status: Open Access ,
Układy poligeneracyjne do skojarzonej produkcji energii elektrycznej, ciepła i chłodu
(Wydawnictwa AGH, 2021) Nowak, Wojciech
The most popular tri-generation solution is the combina- tion of an electricity generator, most often a gas engine, with a heat collection node and an absorption chiller that uses hot water to produce chilled water. Solutions of this type are characterized by high energy efficiency, as well as excellent flexibility of operation, because during the summer the surplus heat produced is used by the absorption chiller to produce cooling, which significantly reduc- es the need for electricity for cooling purposes. The paper presents a system for cogeneration of electricity, heat and cooling with an additional function of water desalination and sewage treatment. The system allows to achieve very high energy efficiency through rational use of waste heat generated by diesel engines.
Access status: Open Access ,
Portal Historia AGH
(Akademia Górniczo-Hutnicza, 2021) Chadaj, Anna; Wijas, Mariusz
Biblioteka Główna
Access status: Open Access ,
Perturbation series for Jacobi matrices and the quantum Rabi model
(Wydawnictwa AGH, 2021) Charif, Mirna; Zieliński, Lech
We investigate eigenvalue perturbations for a class of infinite tridiagonal matrices which define unbounded self-adjoint operators with discrete spectrum. In particular we obtain explicit estimates for the convergence radius of the perturbation series and error estimates for the Quantum Rabi Model including the resonance case. We also give expressions for coefficients near resonance in order to evaluate the quality of the rotating wave approximation due to Jaynes and Cummings.
Access status: Open Access ,
Influence of an Lp-perturbation on Hardy-Sobolev inequality with singularity a curve
(Wydawnictwa AGH, 2021) Ijaodoro, Idowu Esther; Thiam, El Hadji Abdoulaye
We consider a bounded domain $\Omega$ of $\mathbb{R}^{N}$, $N \geq 3$, $h$ and $b$ continuous functions on $\Omega.$ Let $\Gamma$ be a closed curve contained in $\Omega$. We study existence of positive solutions $u \in H^{1}_{0}(\Omega)$ to the perturbed Hardy-Sobolev equation: $-\Delta u+hu+bu^{1+\delta}=\rho^{-\sigma}_{\Gamma} u^{2^*_{\sigma}-1} \quad \textrm{ in } \Omega,$ where $2^*_{\sigma}:=\frac{2(N-\sigma)}{N-2}$ is the critical Hardy-Sobolev exponent, $\sigma \in [0,2)$, $0\lt\delta\lt\frac{4}{N-2}$ and $\rho_{\Gamma}$ is the distance function to $\Gamma$. We show that the existence of minimizers does not depend on the local geometry of $\Gamma$ nor on the potential $h$. For $N=3$, the existence of ground-state solution may depends on the trace of the regular part of the Green function of $-\Delta+h$ and or on $b$. This is due to the perturbative term of order $1+\delta$.
Access status: Open Access ,
Optimized jk-nearest neighbor based online signature verification and evaluation of main parameters
(Wydawnictwa AGH, 2021) Saleem, Muhammad; Kovari, Bence
In this paper, we propose an enhanced $jk$-nearest neighbor ($jk$-NN) algorithm for online signature verification. The effect of its main parameters is evaluated and used to build an optimized system. The results show that the $jk$-NN classifier improves the verification accuracy by 0.73–10% as compared to a traditional one-class $k$-NN classifier. The algorithm achieved reasonable accuracy for different databases: a 3.93% average error rate when using the SVC2004, 2.6% for the MCYT-100, 1.75% for the SigComp'11, and 6% for the SigComp'15 databases. These results followed a state-of-the-art accuracy evaluation where both forged and genuine signatures were used in the training phase. Another scenario is also presented in this paper by using an optimized $jk$-NN algorithm that uses specifically chosen parameters and a procedure to pick the optimal value for $k$ using only the signer’s reference signatures to build a practical verification system for real-life scenarios where only these signatures are available. By applying the proposed algorithm, the average error rates that were achieved were 8% for SVC2004, 3.26% for MCYT-100, 13% for SigComp'15, and 2.22% for SigComp'11.
Access status: Open Access ,
Artificial intelligence approach for detecting material deterioration in hybrid building constructions
(Wydawnictwa AGH, 2021) Česnokov, Andrej Vladimirovič; Mihajlov, Vitalij Vital?evič; Dolmatov, Ivan Viktorovič
Hybrid constructions include heterogeneous materials with different behaviors under load. The aim is to achieve a so-called synergistic effect when the advantages of particular structural elements complement each other in a unified system. The building constructions considered in the research include high-strength steel cables, fiberglass rods, and flexible polymer membranes. The membrane is attached to the rods which have been elastically bent from the initially straight shape into an arch-like form. Structural materials inevitably deteriorate during a long operational period. The present study focuses on detecting material deterioration using Artificial Neural Networks (ANNs), which belong to the scope of intelligent techniques for data analysis. Appropriate ANN structures and required features are proposed. A semi-supervised learning strategy is used. The approach allows the training of the networks with normal data only derived from the construction without defects. Material degradationis detected by the level of reconstruction error produced by the network given the input data. The work contributes to the field of structural health monitoring of hybrid building constructions. It provides the opportunity to detect material deterioration given the forces in particular structural elements.
Access status: Open Access ,
Multifunctional unit for reverse conversion and sign detection based on five-moduli set {2 2n, 2n + 1, 2n − 1, 2n + 3, 2n − 3}
(Wydawnictwa AGH, 2021) Mojahed, Mohsen; Molahosseini, Amir Sabbagh; Zarandi, Azadeh Alsadat Emrani
A high dynamic range moduli set $\{2^{2n}, 2^{n}+1, 2^{n}-1, 2^{n}+3, 2^{n}-3\}$ has recently been introduced as an arithmetically balanced five-modull set for the residue number system (RNS). In order to utilize this moduli set in applications handling signed numbers, two important components are needed: a sign detector, and a signed reverse converter. However, having both of these components results in high-hardware requirements, which makes RNS impractical. This paper overcomes this problem by designing a unified unit that can perform both signed reverse conversion as well as sign detection through the reuse of hardware. To the authors’ knowledge, this is the first attempt to design a sign detector for a moduli set that includes a $\{2^{n}3\}$ moduli. In order to achieve a hardwareamenable design, we first improved the performance of the previous unsigned reverse converter for this moduli set. Then, we extracted a sign-detection method from the structure of the reverse converter. Finally, we made an unsigned reverse converter-to-sign converter through the use of the extracted sign signal from the reverse converter. The experimental results show that the proposed reverse convertor and sign detector result in improvements of 31% and 28% in area and delay, respectively, as compared to the previous unsigned reverse convertor with sign output using a comparator.
Access status: Open Access ,
The modernization of the main fan station of the «Wilson» shaft in KS «Wieliczka» S.A.
(Wydawnictwa AGH, 2021) Pasek, Rafał; Rozwadowski, Krzysztof; Zuski, Zygmunt
This article discusses the modernization of the «Wilson» shaft's main fan station in KS «Wieliczka» S.A., which included: the station building, main fans, the 110 kW electric motors to drive the fans, 3/0.4 kV transformers, 3 kV «Wilson» switchgear, 0.4 kV main switchgear and the communication systems used to control the station.
Access status: Open Access ,
Netflix – the curation of taste and the business of diversification
(Wydawnictwa AGH, 2021) Higson, Andrew
Netflix is considered as a global business invested in strategies of diversification, localisation and personalisation in light of several discourses about the streaming service. One presents Netflix as an evil corporation encouraging binge-watching and reducing individuals to data. A utopian discourse proclaims the democratising potential of digital media technologies, including Netflix’s claims about its personalised, on-demand service. An industry discourse laments Netflix’s disruption of the film and television business. Finally, a scholarly discourse maps the political economy and cultural impact of Netflix. Each discourse attaches a particular cultural value to Netflix. Some offer »antidotes«, including the niche streamers, with their »curated« collections of specialised content. Both types of streamer are in fact gatekeepers regulating access to cultural experiences and promoting particular ideas of taste and diversity. Netflix’s strategies of customisation and glocalisation, and its activities in the Middle East and North Africa, demonstrate in the end that diversity is good for business.
Access status: Open Access ,
Mechanization and automation in the production processes of Polska Grupa Górnicza S.A.
(Wydawnictwa AGH, 2021) Horst, Rajmund; Zdziebko, Jan
In Polska Grupa Górnicza S.A., actions are still being taken to mechanize and automate work, striving to increase production efficiency and reduce the physical burden on miners. Mechanization of works covers further areas which enable the process of automation of underground mining processes. The article presents the leading solutions in the field of mechanization and automation in mine transport, the mechanization of sharing and auxiliary works, and the remote control of belt conveyors and main switchboards. The article also contains a description of the work carried out which support automation processes: activities in the standardization of the equipment of longwall systems, pressure monitoring of powered supports, wireless communication, electronic identification of production assets, and the visualization of the operating parameters of machines and devices.
Access status: Open Access ,
Investigation of aerodynamic parameters of solar plane airfoil using CFD modeling
(Wydawnictwa AGH, 2021) Jaszczur, Marek; Papis, Karolina; Książek, Michał; Czerwiński, Grzegorz; Wojtas, Gabriel; Koncewicz, Wojciech; Nabożna, Sylwia; Wójcik, Marcin
The technology of solar-powered aerial vehicles requires enormous financial support and further development. For this purpose, the computational fluid dynamic can be used. In order to carry out necessary analyses and model development in this research, ANSYS Fluent software was used. Using the first version of the AGH Solar Plane model, preliminary analysis of lift, drag and tearing off the stream was performed. Four new geometries were prepared on which the flattening of upper surfaces for fixing solar panels was tested. The results were validated in the aerodynamic tunnel using particle image velocimetry method. Taking into account all analyses, a number of recommendations have been prepared that will be implemented to create an aircraft, which meets all target requirements.
Access status: Restricted ,
Optymalizacja : wybrane metody z przykładami zastosowań
(Wydawnictwo Naukowe PWN, 2021) Kusiak, Jan; Danielewska-Tułecka, Anna; Oprocha, Piotr; Kusiak, Jan
Access status: Open Access ,
Methods for adjusting the braking force of winders with a traction sheave to prevent the risk of wire rope slippage
(Wydawnictwa AGH, 2021) Celebański, Władysław; Piechota, Piotr
In Koeppe winders, the emergency braking deceleration values must be higher than the values required by mining regulations and lower than the critical deceleration values due to the risk of hoisting rope slippage. Slippage of suspension ropes can lead to damage to the traction sheave lining and, in extreme conditions, serious damage to the shaft hoist. In order to limit the braking force to a safe value, the air or hydraulic oil pressure in the braking systems of winders is regulated during braking. This paper presents methods for adjusting pressure in braking systems during braking and their influence on: the risk of slippage of the suspension ropes, the dynamics of the driving system and the dynamics of the skips themselves. Particular attention was paid to the solution in which the braking force varies during the braking process which can cause large changes in the value of the force acting on the winder.
Access status: Open Access ,
Population diversity in ant-inspired optimization algorithms
(Wydawnictwa AGH, 2021) Byrski, Aleksander; Węgrzyński, Krzysztof; Radwański, Wojciech; Starzec, Grażyna; Starzec, Mateusz; Bargiel, Monika; Urbańczyk, Aleksandra; Kisiel-Dorohinicki, Marek
Measuring the diversity in evolutionary algorithms that work in real-value search spaces is often computationally complex, but it is feasible, however, measuring the diversity in combinatorial domains is practically impossible. Nevertheless, in this paper we propose several practical and feasible diversitymeasurement techniques that are dedicated to ant colony optimization algorithms, leveraging the fact that we can focus on a pheromone table even though an analysis of the search space is at least an NP problem where the direct outcomes of the search are expressed and can be analyzed. Besides sketching out the algorithms, we apply them to several benchmark problems and discuss their efficacy.
Access status: Open Access ,
Generalized powers and measures
(Wydawnictwa AGH, 2021) Burdak, Zbigniew; Kosiek, Marek; Pagacz, Patryk; Rudol, Krzysztof; Słociński, Marek
Using the winding of measures on torus in »rational directions« special classes of unitary operators and pairs of isometries are defined. This provides nontrivial examples of generalized powers. Operators related to winding Szegö-singular measures are shown to have specific properties of their invariant subspaces.
Access status: Open Access ,
Designing walking pathways for a tourist resort with the theory of six value aggregation paths
(Wydawnictwa AGH, 2021) Kowalczyk, Anna Maria
The study examines the possibility of applying the selected components of the theory of six value aggregation paths in designing walking pathways. Based on spatial data collected using a landscape assessment method on the aesthetic values of the landscape of the place under analysis, a model was developed of the network of links of the landscape aesthetic value using a minimum increase in this value. The authors designed scenarios for the optimal routes of walking pathways. The conducted study leads to the conclusion that the minimum value increase path may create a good basis for designing walking pathways. Not only is this manifested in the varied route of the pathway, but also in it being designed in such a way that the landscape's aesthetic value increases beyond an assumed level of aesthetic value. In addition, the use of hexagonal basic fields enables the design of various route lengths and the optimization of time by adapting the model to a specific group of recipients.
Access status: Open Access ,
Novel anchor-selection scheme for distributed mobility management
(Wydawnictwa AGH, 2021) Davaasambuu, Battulga; Telmuun, Tumnee; Sasko, Dominik; Yu, Keping; Sodbileg, Shirmen
The number of subscribers in mobile networks is growing rapidly, which challenges network management and data delivery. Efficient management and routing are key solutions. One important solution is distributed mobility management (DMM), which handles the mobility of subscribers at the edges of mobile networks and load balancing. Otherwise, mobility anchors are distributed across a network that can manage the handover procedures. In this paper, we propose a novel mobility anchor-selection scheme based on the results of a cost function with three factors to select a suitable cell as well as an anchor for moving subscribers and improving the handover performances of networks. Our results illustrate that the proposed scheme provides significantly enhanced handover performance.
Access status: Open Access ,
Calculating capital requirements for operational risk
(Wydawnictwa AGH, 2021) Waschbusch, Gerd; Kiszka, Sabrina
Operational risks have become increasingly important for banks, especially against the background of growing IT dependency and the increasing complexity of their activities. Further-more, the corona pandemic contributed to the increased risk potential. Therefore, banks have to back these risks with own funds. There are currently three measurement approaches for determining the capital requirements for operational risk. In recent years, and especially during the Great Financial Crisis of 2007/2008, however, some of the weaknesses inherent in these approaches have become apparent. Thus, the Basel Committee on Banking Supervision revised the current capital framework. Therefore, this article examines the various measurement approaches, addresses inherent weaknesses and moreover, presents the future measurement approach developed by the supervisory authorities.
Access status: Open Access ,
Hydrothermal ore mineralization from the Polish part of the Tatra Mts., Central Western Carpathians
(Wydawnictwa AGH, 2021) Sitarz, Magdalena; Gołębiowska, Bożena; Nejbert, Krzysztof; Dimitrova, Dimitrina; Milovský, Ratislav
Several areas with hydrothermal ore mineralization are present in the Polish part of the Western Tatra Mts. Massive and disseminated sulfides, mainly minerals from the tetrahedrite group and chalcopyrite, fill quartz veins accompanied by siderite, dolomite and baryte - many of these were mined between the 16$^{th}$ and 18$^{th}$ century. This paper presents information on the mineralogy of the common sulfides and the preliminary studies of both the isotopic composition of sulfur in tetrahedrite as well as the origin of hydrothermal fluids. The most common primary sulfide minerals in the ores are tetrahedrite-(Zn) and tetrahedrite-(Fe) corresponding to Zn ranges from 1.83 to 5.87 wt.% (0.47–1.44 apfu), and Fe from 1.63 to 5.05 wt.% (0.48–1.52 apfu). The substitution of As for Sb shows maximum As content of 7.25 wt.% (1.588 apfu) which corresponds to the Sb/(Sb+As) = 0.60. Both varieties show substitutions of Bi and Hg, up 0.6 wt.% (0.049 apfu) and 0.96 wt.% (0.081 apfu), respectively, and content of trace elements: Co (max. 976 ppm), Cd (max. 735 ppm), In (max. 14 ppm). Chalcopyrite, pyrite, and galena show compositions close to the ideal formula. Differences in the content of trace elements in the studied tetrahedrite and chalcopyrite were explained by element partitioning between these minerals. The distributions of In, Ga and Sn in the studied minerals indicate that the mineralization was formed at low temperature and pressure. The homogenization temperature of the primary inclusions in quartz in the range of 120–174°C indicate the origin of mineralization in low temperature stage from low salinity fluids (up to 17.92 wt.% NaCl eq.). Stable $\delta^{34}S$ isotopes in minerals of the tetrahedrite group suggest that the igneous fluids might be one of the sources from which ores were crystallized.