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The occurrence of surface discontinuous deformations in post-mining areas is currently a significant and important problem, due to both the frequency of their occurrence and the threat they pose to public safety. This paper presents the results of research concerning the possibility of sinkhole formation in the areas of abandoned mining excavations. For the purpose of assessing the condition of the rock mass disturbed by the existence of numerous mining excavations, electrical resistivity tomography investigations were carried out for the selected area where mining was undertaken in the past at shallow depths and many underground workings accessing the deposit exist. The sinkhole hazard was also analysed theoretically with a new original model based on the solution of A. Sałustowicz’s pressure arch theory.

Plate fin-tube heat exchangers are widely used in air conditioning and refrigeration systems and other industry fields. Various errors made in the manufacturing process can result in the formation of an air gap between the tube and fin. Several numerical simulations were carried out for a symmetric section of plate fin-tube heat exchanger to study the influence of air gap on heat transfer under periodic flow conditions. Different locations and sizes of an air gap spanning 1/2 circumference of the tube were considered for the range of airflow velocities. Velocity and temperature fields for cases with air gap were compared with ideal thermal contact cases. Blocking of heat flow by the gap leads to the reduction of heat transfer rate. Fin discontinuity in the front of the tube causes the smallest reduction of the heat transfer rate in comparison to the ideal tube-fin contact, especially for thin slits. The rear gap position is the worst in the smallest gap range. Therefore, reversing the flow direction can lead to up to a 15% heat transfer increase, if mainly the rear gaps are present. The introduction of a thin slit in the front of the tube leads to convective heat transfer enhancement, which should be further investigated.

The accuracy of the moments method is examined by comparison of approximate and exact values of the first three moments of solutions of the aerosol dynamics equation when only condensation and removal are taken into account. The log-normal and γ initial distributions are considered. Errors are expressed in terms of nondimensional independent variables and are found to be small.

The conversion of chemical energy contained in organic matter into electricity has become an object of interest for many scientists worldwide. This technology is used in microbial fuel cells (MFC). Apart from generating electrical energy, these cells can be used simultaneously for wastewater treatment. Although the technology is constantly being improved, currently functioning microbial fuel cells cannot provide appropriate output parameters to use on an industrial scale. One of the barriers is so-called extracellular electron transfer, which in turn depends on the electrode type used, its material, shape, and size. According to current literature, carbon, graphite, stainless steel, and ceramics are the most frequently used electrode materials. However, more and more often, scientists are turning to other, unusual materials, the production of which uses the newest technologies, and one of them is graphene. This material is modified in different ways and connected with other materials, and the results of this seem to be very promising. Scientists manage to get a higher level of extracellular electron transfer and, hence, higher output parameters of the whole system. This article describes chosen technologies and attempts made by scientists worldwide to use graphene in MFC and their results.

Determination of power quality becomes more and more important in the future. Low voltage networks are usually large and very complex. Therefore the calculation of power quality parameters by modeling as equivalent network is hardly possible in practice. That's why new methods for efficient and exact estimation of power quality parameters in low voltage networks are necessary. The presented method is based on the fact that networks of similar structure have a similar behavior in power quality. The Points of Common Coupling (PCC) are divided into different classes, where each class consists of PCC's with similar characteristics. This way the method allows the estimation of power quality levels based on the class a PCC is assigned to. The paper demonstrates the method for the 5th voltage harmonic as an example power quality parameter. The above-mentioned classification of substations is based on probabilistic neural networks.

Preparation of TiO2 using the hydrothermal treatment in NH4OH solution and subsequent thermal heating at 500–700 °C in Ar was performed in order to introduce some titania surface defects. The highest amount of oxygen vacancies and Ti3+ surface defects were observed for a sample heat-treated at 500 °C. The presence of these surface defects enhanced photocatalytic properties of titania towards the deactivation of two bacteria species, E. coli and S. epidermidis, under artificial solar lamp irradiation. Further modification of TiO2 was targeted towards the doping of Cu species. Cu doping was realized through the impregnation of the titania surface by Cu species supplied from various copper salts in an aqueous solution and the subsequent heating at 500 °C in Ar. The following precursors were used as a source of Cu: CuSO4, CuNO3 or Cu(CH3COO)2. Cu doping was performed for raw TiO2 after a hydrothermal process with and without NH4OH addition. The obtained results indicate that Cu species were deposited on the titania surface defects in the case of reduced TiO2, but on the TiO2 without NH4OH modification, Cu species were attached through the titania adsorbed hydroxyl groups. Cu doping on TiO2 increased the absorption of light in the visible range. Rapid inactivation of E. coli within 30 min was obtained for the ammonia-reduced TiO2 heated at 500 °C and TiO2 doped with Cu from CuSO4 solution. Photocatalytic deactivation of S. epidermidis was greatly enhanced through Cu doping on TiO2. Impregnation of TiO2 with CuSO4 was the most effective for inactivation of both E. coli and S. epidermidis.

Ustawa z dnia 20 lutego 2015 r. o odnawialnych źródłach energii wprowadziła pojęcie spółdzielni energetycznych, określiła ich sposób działania i procedury zakładania oraz prowadzenia. Po ośmiu latach od dnia ogłoszenia tej regulacji w wykazie spółdzielni energetycznych figuruje sześć spółdzielni energetycznych (zgodnie ze stanem na dzień 3 marca 2023 r.). W związku ze skromnym dorobkiem praktyki gospodarczej w Polsce w tworzeniu spółdzielni energetycznych można wysunąć wniosek, że zaproponowany przez ustawodawcę konstrukt spółdzielni energetycznej jest wadliwy lub niekonkurencyjny w stosunku do innych rozwiązań dostępnych na rynku. Zastanawiającym jest, że mimo tak ogólnie widocznych tendencji dążących do wspierania inicjatyw w zakresie budowy w Polsce systemu energetycznego opartego na OZE, której istotnym elementem mogłyby być spółdzielnie energetyczne, ustawodawca skonstruował (i do dziś nie znowelizował) tak nieprzystępną i nieprzystosowaną do realiów społeczno-ekonomicznych koncepcję zrzeszenia prosumentów. Głównym celem poznawczym badania jest odpowiedź na pytanie, dlaczego taka koncepcja spółdzielczości energetycznej de facto nie przyjęła się w ciągu ostatnich ośmiu lat w Polsce. Przedmiotowe studium skupia się na scharakteryzowaniu osiowych problemów koncepcji spółdzielni energetycznej w warunkach polskich w obecnym stanie prawnym. Pod uwagę wzięte zostały w szczególności czynniki ekonomiczne, prawne i społeczne, uznane przez autora za szczególnie istotne. Podstawę analizy stanowi głównie ustawodawstwo, ponieważ w materii spółdzielczości energetycznej dorobek praktyki, na którym można by oprzeć szerszą analizę komparatywną, ze względów wymienionych powyżej jest znikomy.