The article examines the trends in social communication in Poland in 1980–1981. Having analyzed multiple sources and research studies, the author comes to the conclusion that in this watershed period in Polish postwar history was characterized not only by stricter control of the official information channels but also a grassroot pushback manifested in the rise of uncensored bulletins, leaflets and propaganda posters.
This article presents the role and thematic content of the Rocznik Historii Prasy Polskiej [ Yearbook of the History of Polish Press] (1998–2022), especially the period 2018–2022.
This article contains a bibliometric analysis and an overview of the lifetime achievement of Jerzy Leonard Myśliński (1934–2022). He authored 287 academic publications devoted mostly to media history (81%), including 25 monographs, 30 studies published in collective works, and more than 232 articles and reviews. A citation analysis of his contributions shows that Jerzy Leonard Myśliński ranks as one of the most highly cited historians of the Polish press in 1960–2010.
The purpose of the article is to analyze the impact of local press on social capital. A content analysis of Gazeta Lipnicka, a newspaper published between 1997 and 2016 in Bielsko-Biała by the Lipnik Association, is used to examine its communicative and integrative role in the local community.
This is a report on the work of the Commission of Press Studies of the Cracow Branch of the Polish Academy of Sciences in 1973–2022. Based on archive materials, it presents the Commission's origins, profile, function-ing, membership statistics and members' affiliations, and its coverage of an evolving research scene.
This paper describes results of tensile mechanical strength testing of two types of composite suspension line insulators from two manufacturers. In order to take into account the operation of composite insulators in overhead transmission lines with high-temperature low-sag (HTLS) conductors, the testing of their static and fatigue strength was performed at both ambient and elevated temperatures. The results showed that the static mechanical strength of composite insulators decreased with an increase in the temperature of the lower end fitting of the insulator, and proved that it followed a third-degree polynomial function. Calculations performed demonstrated that a significant cause of reduction in strength was the increase in the radial stress following the temperature increase in the crimped glassepoxy resin core of the insulator. The results of the fatigue strength testing demonstrated that the increase in the temperature of the lower end fitting of the insulator up to 85°C degree had a little effect on the fatigue strength of the tested composite insulators.
This elaboration presents the concept of a unidirectional DC–DC switchedcapacitor converter operating as a voltage tripler. The system consists of two resonant cells with switched capacitors and chokes. This proposed converter topology achieves low voltages on semiconductor switches (diodes and transistors) compared to the classic SC series-parallel converter or the boost topology. The output voltage on the capacitors is reduced in the proposed converter because it is divided into two series-connected capacitors with asymmetric distribution. The presented results describe the analytical description of the system operation and the analytical equation for semiconductor currents. A simulation and experimental results have been performed. The system efficiency and three voltage gain values were measured in the experimental setup. The efficiency measured was also compared with the analytical determination curve for loss analysis and further converter optimization.
This study presents a method to directly calculate the stator current Fourier spectra in double-cage induction motors to diagnose faults in rotor cages. A circuit model is developed for this purpose, allowing the modelling of any asymmetry in the outer and inner rotor cages. The model extends the conventional model of a cage motor by considering the higher space harmonics generated by the stator windings. The asymmetry of the cages is modelled by growing the resistance of any of the rotor bars. This results in various model equations, to be solved by looking for diagnostic signals. Motor current signature analysis is typically used to diagnose cage motors based on the Fourier spectra of the stator currents during steady-state operation. This study determines these spectra for double cage motors using the harmonic balance method, omitting the transient calculations. The calculation results confirmed the sensitivity of the stator current Fourier spectra as a diagnostic signal to distinguish faults in the outer and inner cages.
Department of Electrical Engineering, Faculty of Electrical and Computer Engineering, Cracow University of Technology, 24 Warszawska str., 31-155 Kraków, Poland
This paper presents an analysis of electric vehicle charging station operation based on a dual active bridge topology. Two cases are considered: one with the use of a medium frequency planar transformer, the other with a conventional Litz winding transformer. An analysiswas performed using both solutions in order to compare the performance characteristics of the system for both cases and to present the differences between each transformer solution. The analysis was based on tests carried out on the full-scale model of an electric vehicle charging station, which is the result of the project "Electric vehicle charging system integrated with lighting infrastructure" realized by the Department of Drives and Electrical Machines, Lublin University of Technology. The results presented in the paper show that the conventional transformer used in the research achieved better results than the planar transformer. Based on the results obtained, the validity of using both solutions in electric vehicle charging stations was considered.
The low frequency ripple of the input side current of the single-phase inverter will reduce the efficiency of the power generation system and affect the overall performance of the system. Aiming at this problem, this paper proposes a two-modal modulation method and its MPC multi-loop composite control strategy on the circuit topology of a single-stage boost inverter with a buffer unit. The control strategy achieves the balance of active power on both sides of AC and DC by controlling the stable average value of the buffer capacitor voltage, and provides a current reference for inductance current of the DC input side. At the same time, the MPC controller uses the minimum inductor current error as the cost function to control inductor current to track its reference to achieve low frequency ripple suppression of the input current. In principle, it is expounded that the inverter using the proposed control strategy has better low frequency ripple suppression effect than the multi-loop PI control strategy, and the conclusion is proved by the simulation data. Finally, an experimental device of a single-stage boost inverter using MPC multi-loop composite control strategy is designed and fabricated, and the experimental results show that the proposed research scheme has good low frequency ripple suppression effect and strong adaptability to different types of loads.
For a solar photovoltaic power system on a university campus, the electricity generated by the system meets the campus load, and the extra electricity is delivered to the grid. Generally, the price of the photovoltaic system is cheaper than that of the utility power system. The full use of solar electricity can reduce the electricity cost of the school. The deep belief network is used to predict solar photovoltaic generation and electricity load, and the gap is found. According to the gap, the power loads on the campus are adjusted to improve the utilization rate of solar power generation. Through the practical application of Changqing Campus of Qilu University of Technology in China, it is found that the utilization rate of solar photovoltaic power generation effectively improved from 91.24% in 2017 to 98.16% in 2019, and the annual electricity is saved by 68 610 yuan (in 2019).
School of Information and Automation Engineering, Qilu University of Technology (Shandong Academy of Sciences), No. 3501, Daxue Road, Changqing District, Jinan 250353 Shandong Province, PR China
This paper investigates the possibilities for developing a pole-changing winding with a pole ratio of 3:4 with improved electromagnetic properties. Such a winding can be used in two-speed induction motors for turbo mechanisms. The scheme of the new winding was obtained by using a discretely-specified spatial function method developed at the Tashkent State Technical University. A comparison of the parameters obtained for a similar winding received by the pole amplitude modulation method has been presented. Design of a new motor with a new winding is developed based on the standard induction motor. The paper presents results of laboratory tests, too.
Rare-earth permanent magnets are coated in order to avoid corrosion. When considering the rated geometrical properties of a sample, the coating thickness has to be known precisely as it wrongly enlarges the magnetically active volume which in turn affects the accuracy of the measured magnetic properties. In this work, the sensitivity of hard magnetic material property measurements regarding the consideration of different coating thicknesses is evaluated. Moreover, the impact of eddy current effects on the magnetic properties is studied when measuring in an open circuit. Additionally, an outlook for a measurement-based determination of the electric conductivity of permanent magnet samples is given.
The article presents selected issues related to the development and testing of the diagnostics systems dedicated for superconducting electromagnets. The systems were constructed to assess the production quality of superconducting electromagnets of the SIS100 synchrotron, a new accelerator being built as part of the Facility of Antiproton and Ion Research (FAIR). One of the systems is used for automatic checking of electrical connection parameters and the continuity of electric circuits. The role of the second device is to assess the quality of winding insulation and to estimate circuit parameters of electromagnet coils using the capacitor discharge method. The work presents measurements and analysis of current and voltage waveforms acquired during discharges on a magnet coil simulator and on the SIS100 main dipole electromagnet.
In the last decade, there has been a substantial surge in the advancement of research into the maximum power point tracking (MPPT) controller. The MPPT approaches, on the other hand, continue to be in high demand due to the ease and simplicity with which tracking techniques can be implemented on the maximum power point (MPP). Diverse MPPT approaches and their modifications from various literature are categorized and thoroughly explored in this work, which is divided into two sections. The discussions are centered on the primary goal of attaining the most extraordinary feasible MPPT technique that produces the best results at the lowest possible expense. In order to determine which MPPT approaches to use, evaluations from earlier literature are used to guide the decision. In this section, we will examine the evaluation of the MPPT technique in two sections. Previously, in Part I, we explored the MPPT techniques based on constant parameters and trial-and- error. Part II of this article will examine the MPPT technique, which is based on mathematical computation, measurement, and comparison, and the algorithm development that has occurred in recent years. Furthermore, this section’s assessment for selecting MPPT approaches is based on previous literature reviews. To aid with this selection, the following criteria for the MPPT approach are proposed: sensors and analog/digital requirements, costeffectiveness, simplicity, stability, efficiency, and tracking speed. This enables the reader to select the MPPT technique that is most appropriate for their application.
Electromagnetic forces generated by the short circuit current and leakage flux in low- and high-voltage windings of distribution transformers as well as amorphous core transformers will cause the translation, destruction, and explosion of the windings. Thus, the investigation of these forces plays a significant role for researchers and manufacturers. Many authors have recently used the finite element method to analyze electromagnetic forces. In this paper, an analytic model is first developed for magnetic vector potential formulations to compute the electromagnetic forces (i.e., axial and radial forces) acting on the low- and high-voltage windings of an amorphous core transformer. The finite element technique is then presented to validate the results obtained from the analytical model. The developed model is applied to an actual problem.
This paper proposes a new fault location method in radial medium voltage distribution networks. The proposed method only uses the measurement data at the feeder beginning to approximate the characteristic equation showing the dependence between the positive-sequence voltage and phase angle at the monitoring point with the distance to the fault location for each fault type on each line segment. To determine these characteristic equation coefficients, the entire distribution network will be modeled and simulated by four types of faults at different locations along the lines to build the initial database. Based on this database, the mathematical functions in MATLAB software are applied to approximate these coefficients corresponding to each type of fault for each line segment in the network. Then, from the current and voltage measurement data at the feeder beginning, the algorithms of global search, comparison, and fault ranking are used to find out where the fault occurs on the distribution network. Two types of distribution network with and without branches are studied and simulated in this paper to verify and evaluate the effectiveness of the proposed method.
In this work we discussed the safety of the electric field environment in the No.3 carriage where the pantograph is located. DSA380 pantograph, CRH5 EMU carriage and passengers’ models were established to study the electric field exposure of passengers at different positions. The results showed that Emax in the carriage without passengers is 1.173 x 10 6 mV/m. Then we set the passengers’ positions according to the electric field distribution in the carriage without passengers and obtained that Emax in the carriage with passengers is 3.195 x 10 6 mV/m. It can be seen that the maximum induced electric field intensity of passengers at different positions appears on the soles of shoes, the maximum value is 3.028 x 105 mV/m, the maximum induced current density occurs at the ankle, its maximum value is 3.476 x 10 -5 A/m 2. It can be concluded that the maximum induced electric field intensity of passenger’s head appears in the cerebrospinal fluid area, with a maximum value of 202.817 mV/m, and the maximum induced electric field intensity of passenger’s head at the door is larger than that in the middle of the carriage. The maximum values of the induced electric field intensity in all tissues of passengers are much smaller than the basic limits of electromagnetic exposure to the public set by the International Commission on Non-Ionizing Radiation Protection (ICNIRP). This study indicated that the pantograph has little influence on the electric field environment in the carriage under working state, and will not cause any health hazard to the passengers in this working frequency electric field environment.
As the capacity and scale of distribution networks continue to expand, and distributed generation technology is increasingly mature, the traditional fault location is no longer applicable to an active distribution network and "two-way" power flow structure. In this paper, a fault location method based on Karrenbauer transform and support vector machine regression (SVR) is proposed. Firstly, according to the influence of Karrenbauer transformation on phase angle difference before and after section fault in a low-voltage active distribution network, the fault regions and types are inferred preliminarily. Then, in the feature extraction stage, combined with the characteristics of distribution network fault mechanism, the fault feature sample set is established by using the phase angle difference of the Karrenbauer current. Finally, the fault category prediction model based on SVR was established to solve the problem of a single-phase mode transformation modulus and the indistinct identification of two-phase short circuits, then more accurate fault segments and categories were obtained. The proposed fault location method is simulated and verified by building a distribution network system model. The results show that compared with other methods in the field of fault detection, the fault location accuracy of the proposed method can reach 98.56%, which can enhance the robustness of rapid fault location.
Indium gallium zinc oxide (In–Ga–Zn–O) thin films, which are transparent conductive films for liquid crystals and electroluminescent displays, were fabricated via singlestep sputter deposition using one target containing different proportions of indium oxide, gallium oxide, and zinc oxide powders. Experimental results suggest that the In–Ga–Zn–O thin films can be prepared using the method of single-step radio frequency (RF) sputter deposition, applying a powder target containing indium oxide, gallium oxide, and zinc oxide. The In–Ga–Zn–O thin films were prepared on Si substrates, and the deposition rate depended on the target composition. In these plasma processes, electron density and temperature were essentially independent of target composition. The prepared films were very smooth with a root-mean-square roughness of less than 10 nm. The crystallinity of the ZnO peak was observed in all the films; whereas the In and Ga peaks were not observed in the films prepared. The X-ray photoelectron spectroscopy of the films also revealed that the elemental concentration ratio of In–Ga–Zn–O thin films could be prepared using one target, and that can be easily controlled by ratios in the In 2O 3/Ga 2O 3/ZnO composition in the powder target. The transmittances were > 75% at 800 nm for all the target mixtures, and increased with increasing In 2O 3 in the powder target.
Graduate School of Engineering Sojo University, Ikeda Nishi-ku Kumamoto City, Japan
Department of Electrical and Electronic Engineering, National Institute of Technology, Sasebo College, Okishin-machi, Sasebo City, Nagasaki Pref., Japan
en
pl
