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The Influence of Dielectric Properties on Heating of Sulphide Ores in Electromagnetic Field
(Polish Mineral Engineering Society, 2024-01-06) Znamenackova, Ingrid; Dolinská, Silvia; Láčík, Jaroslav; Hredzák, Slavomír; Briančin, Jaroslav
Microwave heating is a form of high-frequency electromagnetic radiation. The heating of primary and secondary mineral raw materials in the microwave field depends primarily on their dielectric and thermal properties. The condition is the absorption of microwave radiation. Dielectric heating of materials occurs immediately after placing them in an electric high-frequency field. Knowledge of the dielectric characteristics of mineral raw materials is an important assumption for the use of electromagnetic radiation at the intensification of technological treatment methods. Most mined minerals consist of several mineral components that have different dielectric properties. Most sulphides are well heated in a microwave field. Conversely, tailings components of ores, such as quartz, are transmission materials. The study of dielectric properties involves measurements of the complex relative permittivity *, which consists of a real and an imaginary part. The imaginary part of permittivity “loss factor” represents the measure of dielectric losses in the material. Microwave heating of sulphide ores and concentrates such are chalcopyrite, tetrahedrite, galena depends on their chemical composition and content of impurities. The article describes the influence of dielectric properties on heating of chalcopyrite in microwave field. SEM analyses of studied samples are presented.
Performance Evaluation of Objective Quality Assessment Methods for Omnidirectional Images Under Emerging Compressions
(IEEE, 2024-10-11) Šimka, Marek; Polák, Ladislav; Novotný, Martin; Kufa, Jan; Fliegel, Karel
This paper presents a unique study of objective and subjective image quality assessment (IQA) of 360 degrees images, distorted by emerging and legacy compressions - AV1 Image File Format (AVIF), Joint Photographic Experts Group (JPEG), High Efficiency Image File Format (HEIC), JPEG XL from the cross-lab experiments carried out by two universities. The performance evaluation of objective conventional IQA methods relied on statistical data analysis employing not only traditional approaches with correlation coefficients but also advanced techniques such as Receiver Operating Characteristic (ROC) analysis, which offers several statistical advantages. The comprehensive statistical examination presented, utilizing an outcome from the subjective experiment with 66 observers, confirmed that the performance of specific IQA metrics depends not only on the image features but also on the applied image compression algorithm. Overall, the study examined nine IQA objective metrics. For instance, when evaluating distortion caused by the AVIF and HEIC codecs, the Multi-Scale Structural Similarity (MS-SSIM) metric exhibited the best performance, while the Feature Similarity chrominance (FSIMc) metric excelled in assessing JPEG-based compressions. Additionally, detailed outcomes of the subjective experiments, including eye-tracking data, are available in a public dataset. This study provides previously unexplored insights into the performance of conventional objective metrics for 360 degrees images degraded by emerging image codecs. The presented results suggest suitable metrics for specific application scenarios (codecs) and, along with the dataset, lay the groundwork for further research on new objective quality assessment methods for omnidirectional images under emerging compressions.
Comparison of Analytical and Algorithm-Based Design of Two-Port Using Two Bilinear Sections
(IEEE, 2024-07-29) Semenov, Dmitrii; Šotner, Roman; Polák, Ladislav; Jeřábek, Jan; Petržela, Jiří; Langhammer, Lukáš
This paper compares the analytical approach and optimization algorithm for designing a two-bilinear-section-based two-port transfer function hinged on a numerical sweep with the intention of implementing fractional-order (FO) systems in many sensing areas. The study compares analytical and algorithm-based design approaches and tests their effectiveness in designing a two-port system that accommodates phase shifts within the 10 degrees to 80 degrees range and with various phase ripple limits. The impact of phase changes on usable bandwidth (yield maximization) is also explored. The proposed algorithm represents the most optimal approach and calculates zeros/poles frequencies to precisely keep the required mean phase value and phase ripple value for the defined center frequency. Experimental results are provided, utilizing two bilinear sections featuring the current feedback amplifier. Moreover, the implementation of the novel two-port Cole model as an application example of the proposed design is presented and evaluated. The approaches presented are useful in sensing, modeling, and instrumentation.
Chaotic systems based on higher-order oscillatory equations
(NATURE PORTFOLIO, 2024-09-10) Petržela, Jiří
This paper discusses the design process toward new lumped chaotic systems that originates in higherorder ordinary differential equations commonly used as description of ideal oscillators. In investigated thirdorder case, two chaotic oscillators were constructed. These systems are dual in the sense of vector field geometry local to fixed points. The existence of robust chaos was proved by both standard routines of numerical analysis and practical measurement. For the fourthorder oscillatory equation, the concept based on interaction between superinductor and supercapacitor was examined in detail. Since both “superelements” are active, the nonlinearity essential to the evolution of chaos is fully passive. It is demonstrated that complex motion is robust and does not represent long transient behavior or numerical artefact. The existence of chaos was verified using standard quantifiers of the flow, such as the largest Lyapunov exponents, recurrence plots, approximate entropy and sensitivity calculation. A good final agreement between theoretical assumptions and practical results will be concluded, on a visual comparison basis.
Survey on 5G Physical Layer Security Threats and Countermeasures
(MDPI, 2024-08-26) Harvánek, Michal; Bolcek, Jan; Kufa, Jan; Polák, Ladislav; Šimka, Marek; Maršálek, Roman
With the expansion of wireless mobile networks into both the daily lives of individuals as well as into the widely developing market of connected devices, communication is an increasingly attractive target for attackers. As the complexity of mobile cellular systems grows and the respective countermeasures are implemented to secure data transmissions, the attacks have become increasingly sophisticated on the one hand, but at the same time the system complexity can open up expanded opportunities for security and privacy breaches. After an in-depth summary of possible entry points to attacks to mobile networks, this paper first briefly reviews the basic principles of the physical layer implementation of 4G/5G systems, then gives an overview of possible attacks from a physical layer perspective. It also provides an overview of the software frameworks and hardware tool-software defined radios currently in use for experimenting with 4G/5G mobile networks, and it discusses their basic capabilities. In the final part, the paper summarizes the currently most promising families of techniques to detect illegitimate base stations-the machine-learning-based, localization-based, and behavior-based methods.

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