Non-intentionally doped GaSb epilayers were grown by molecular beam epitaxy (MBE) on highly mismatched semi-insulating GaAs substrate (001) with 2 offcut towards (110). The effects of substrate temperature and the Sb/Ga flux ratio on the crystalline quality, surface morphology and electrical properties were investigated by Nomarski optical microscopy, X-ray diffraction (XRD) and Hall measurements, respectively. Besides, differential Hall was used to investigate the hole concentration behaviour along the GaSb epilayer. It is found that the crystal quality, electrical properties and surface morphology are markedly dependent on the growth temperature and the group V/III flux ratio. Under the optimized parameters, we demonstrate a low hole concentration at very low growth temperature. Unfortunately, the layers grown at low temperature are characterized by wide FWHM and low Hall mobility.

The paper presents the first vertical-cavity surface-emitting lasers (VCSELs) designed, grown, processed and evaluated entirely in Poland. The lasers emit at »850 nm, which is the most commonly used wavelength for short-reach (<2 km) optical data communication across multiple-mode optical fiber. Our devices present state-of-the-art electrical and optical parameters, e.g. high room-temperature maximum optical powers of over 5 mW, laser emission at heat-sink temperatures up to at least 95°C, low threshold current densities (<10 kA/cm2) and wall-plug efficiencies exceeding 30% VCSELs can also be easily adjusted to reach emission wavelengths of around 780 to 1090 nm.

This paper presents the results of a numerical analysis of nitride-based edge-emitting lasers with an InGaN/GaN active region designed for continuous wave room temperature emission of green and blue light. The main goal was to investigate whether the indium thin oxide (ITO) layer can serve as an effective optical confinement improving operation of these devices. Simulations were performed with the aid of a self-consistent thermal-electrical-optical model. Results obtained for green- and blue-emitting lasers were compared. The ITO layer in the p-type cladding was found to effectively help confine the laser mode in the active regions of the devices and to decrease the threshold current density.

Shale gas mining is mainly viewed as an industrial and economic issue. But we can also look at it from the scientific perspective. Why should we?

In this study, an analysis of the optical performance of two types of distributed Bragg reflector structures based on GaAs and InP material systems was carried out. The structures were designed for maximum performance at 4 µm with their reflectivity achieving between 80 and 90% with eight pairs of constituent layers. To further enhance the performance of these structures, additional Au layers were added at the bottom of the structure with Ti pre-coating applied to improve the adhesivity of the Au to the semiconductor substrate. The optimal range of Ti layer thickness resulting in the improvement of the maximum reflectivity was determined to be in between 5 and 15 nm.

The paper presents a study of the performance of some selected UV detectors. Unlike many similar works, the obtained data refer to commercial photodiodes (not only to detector materials). The main task of the research was to determine the influence of the operating temperature and annealing on the detector spectral responsiveness. A comparison of the results obtained for the photodiodes made of GaN and SiC was also performed. Although both kinds of detectors can work at high temperatures for a long time, some modification of their properties was observed. However, for GaN and SiC photodiodes, this modification has a substantially different nature. It is very important for some applications, e.g. fire alarms and a military equipment.

This paper concerns measurements and calculations of low frequency noise for semiconductor layers with four-probe electrodes. The measurements setup for the voltage noise cross-correlation method is described. The gain calculations for local resistance noise are performed to evaluate the contribution to total noise from different areas of the layer. It was shown, through numerical calculations and noise measurements, that in four-point probe specimens, with separated current and voltage terminals, the non-resistance noise of the contact and the resistance noise of the layer can be identified. The four-point probe method is used to find the low frequency resistance noise of the GaSb layer with a different doping type. For n-type and p-type GaSb layers with low carrier concentrations, the measured noise is dominated by the non-resistance noise contributions from contacts. Low frequency resistance noise was identified in high-doped GaSb layers (both types). At room temperature, such resistance noise in an n-type GaSb layer is significantly larger than for p-type GaSb with comparable doping concentration.

We investigated the germination requirements of Androsace villosa L. (Hairy Androsace), which spreads on limestone or granite screes or ledges of rocky or turfy slopes and hilltops of the alpine zone. With seeds collected from Uludag Mt. (Bursa, Turkey, 2200-2300 m a.s.l.), germination was studied in fresh seeds, seeds subjected to short-time moist chilling (15 d, +4°C), to GA3 (100, 150 and 250 ppm), and to chilling plus GA3. The hormone and moist chilling treatments were carried out in continuous darkness (20°C) and under a 12 h photoperiod at 20/10°C. Seeds maintained in darkness gave higher germination percentages than seeds maintained under a photoperiod. Germination rates rose to 90-97% with 100-250 ppm GA3 and short-time moist chilling in continuous darkness (20°C). Seeds germinated rapidly under a combination of GA3 and short-time moist chilling in continuous darkness, generally giving the lowest mean germination times (4.4-5.0 d) among the treatments.

In this paper, dynamic response improvement of the grid connected hybrid system comprising of the wind power generation system (WPGS) and the photovoltaic (PV) are investigated under some critical circumstances. In order to maximize the output of solar arrays, a maximum power point tracking (MPPT) technique is presented. In this paper, an intelligent control technique using the artificial neural network (ANN) and the genetic algorithm (GA) are proposed to control the MPPT for a PV system under varying irradiation and temperature conditions. The ANN-GA control method is compared with the perturb and observe (P&O), the incremental conductance (IC) and the fuzzy logic methods. In other words, the data is optimized by GA and then, these optimum values are used in ANN. The results are indicated the ANN-GA is better and more reliable method in comparison with the conventional algorithms. The allocation of a pitch angle strategy based on the fuzzy logic controller (FLC) and comparison with conventional PI controller in high rated wind speed areas are carried out. Moreover, the pitch angle based on FLC with the wind speed and active power as the inputs can have faster response that lead to smoother power curves, improving the dynamic performance of the wind turbine and prevent the mechanical fatigues of the generator.

This paper presents an improved approach for locating and identifying faults for UHV overhead Transmission line by using GA-ANFIS. The proposed method uses one end data to identify the fault location. The ANFIS can be viewed either as a Fuzzy system, neural network or fuzzy neural network FNN. The integration with neural technology enhances fuzzy logic system on learning capabilities are proposed to analyze the UHV system under different fault conditions. The performance variation of two controllers in finding fault location is analyzed. This paper analyses various faults under different conditions in an UHV using Matlab/simulink. The proposed method is evaluated under different fault conditions such as fault inception angle, fault resistance and fault distance. Simulation results confirm that the proposed method can be used as an efficient for accurate fault location on the transmission line.

There are many IT tools available on the market that carry out various types of forecasts in the gas industry. Programming evolves with the availability and capability of computers. IT tools support the user in engineering calculations, but also present the obtained results in an interesting visualization, e.g. in the form of interactive charts. The software can support making business decisions, which, in turn, can be used as business intelligence. In the era of digitization, huge metadata of measurements are created, so conducting data analyzes in the energy sector is very common. Moreover, rapidly evolving artificial intelligence creates new opportunities. The article presents a sample analysis of calculations using RStudio, an integrated development environment for the R language, a programming language for statistical calculations and graphics. The aim of the article is to present the possibility of using R language software to make a forecast and to determine the quality of forecasts. The article aims to present the possibility of making forecasts based on mathematical models available in R packages and the possibilities offered by the forecasting platform to readers. The article presents the U.S. market and has a particular focus on Natural Gas Residential Consumption in Pennsylvania (publicly available data from the U.S. Energy Information Administration). This dataset represents the monthly consumption of natural gas between 2015 and 2020. Forecasts were presented over a span of 12 months.

Technologia HTAC (High Temperature Air Combustion) jest jednym z najważniejszych osiągnięć w technice spalania w ostatnich latach. Jej ideą jest taka organizacja procesu spalania, aby reakcja zachodziła w calcj objętości komory spalania przy wyrównanych profilach temperatury i koncentracji. Może to być zrealizowane poprzez podgrzanie powietrza powyżej temperatury zapłonu paliwa, oddzielenie dysz powietrza i paliwa i wysoką recyrkulację spalin wewnątrz komory spalania. Wyrównana i umiarkowana temperatura we wnętrzu komory pozwala na osiągnięcie niskiej emisji NO a z drugiej strony dostatecznie długi czas pobytu owocuje niską emisją CO. W niniejszej pracy autorzy przedstawiają model matematyczny pozwalający ilościowo ująć wpływ temperatury powietrza oraz stopnia recyrkulacji na końcowa emisję NO i CO.

The formation, migration and volume distribution of gas clouds, which are dominated by natural gas after oil and gas leakage, are the material basis of fire and explosion accidents on offshore platforms. Based on an offshore platform as the background, this paper conducts research on the gas cloud using numerical simulation method, the selection of different wind speeds, leak leakage rate of quality, wind direction and the direction angle, the leakage of gas diffusion behaviour simulation studies and its size distribution. There is a “coupling” effect on the volume value of 5% CH4 cloud between different wind speeds, leakage mass rates, and wind direction and leakage direction. When the wind speed is 13 m/s, the leakage mass velocity is 8 kg/s, and the included angle between wind direction and leakage direction is 180°, the “coupling” effect on the volume value of 5% CH₄ cloud increases significantly. The above research results can provide a reference for the reasonable division of process risk area, firewall design and quantitative risk assessment of fire and explosion of an offshore platform.

New model of the simulation of the airbag inflation process, taking into account the influence of the airbag environment on the folding process, have been proposed. Equations describing a new model and the used numerical schemes were presented. The differences of the airbag fabric skin motion during the folding process, obtained by the use of different process models (existing and proposed), have been presented on the simple geometry examples. From the analysis of obtained results one acknowledged that the proposed model should be used in all calculations of the airbag operation in non-typical situations, out-of position occupants, side airbags, particularly in the case of small distances between the closed airbag and the elements of the body of the protected person.

As is well known, gas consumption and its prices depends on many factors including local factors, geopolitics, the development of the gas transport infrastructure (including liquefied natural gas), distribution and extraction costs – for example unconventional deposits (e.g. shale gas). The global gas market depends primarily on the economic relations between large gas producers and importers e.g. US-China, Middle East/US – Russia etc. (Olayele 2015). In individual countries, the price is also dependent on concluded contracts and delivery directions. Also it should be mentioned that the gas consumption depends on weather conditions, type of day of the year (holiday, business day, month) and economic situation (Kosowski et. al 2010). What impact has the appearance of the COVID-19 epidemic had on the European natural gas market?

The analyzed research problem concerned, in particular, two areas: gas consumption and its prices, in selected European countries in the aspect of the spread of the COVID-19 epidemic with reference to historical data from 2016–2019. Seven European countries belonging to the European Network of Transmission System Operators for Gas (ENTSOG) were selected, for which the highest inland consumption of natural gas by country was observed in the last year. The countries are presented in order or consumption: Germany, the United Kingdom, Italy, France, the Netherlands, Spain, Poland. The data has been downloaded from transmission system operators (TSOs) for each of these countries.

Furthermore the article showed information about the dates of governments restrictions (lockdown), LNG contract volumes, injection/withdrawal volumes (storage).

Potraktowanie zużycia paliwa w kotłowni jako szeregu czasowego daje możliwość użycia do analizy tego zjawiska narzędzi odpowiednich do przetwarzania takich danych. Jednym z nich są modele ARIMA. W artykule zaproponowano wykorzystanie tego typu modeli do prognozowania miesięcznego zużycia gazu w kotłowni pracującej na potrzeby ogrzewania i przygotowania ciepłej wody. Kotłownia zasila w ciepło grupę budynków mieszkalnych. Na podstawie zebranych danych pomiarowych wytypowano trzy konkretne modele, dla których przeprowadzono ocenę trafności prognozy. Obliczenia i analizy zostały przeprowadzone w środowisku R przy zastosowaniu pakietów forecast oraz ggplot2. Wykazana została dobra jakość uzyskanych prognoz, potwierdzająca przydatność zaproponowanych narzędzi analitycznych. W podsumowaniu artykułu wskazano również, do jakich celów można wykorzystać uzyskane w ten sposób prognozy. Mogą one być przydatne do diagnostyki poprawności działania źródła ciepła. Zarejestrowanie zużycia paliwa na poziomie poważnie odbiegającym od prognozy powinno być jednoznaczną przesłanką do niezwłocznego przeprowadzenia diagnozy stanu pracy kotłowni i całego systemu zaopatrzenia w ciepło oraz wyjaśniania przyczyny tej różnicy. W ten sposób można doprowadzić do wykrycia nieprawidłowości w działaniu systemu zaopatrzenia w ciepło, na długo przed stwierdzeniem ich tradycyjnymi metodami. Prognoza zużycia gazu jest też przydatna do optymalizacji zarządzania finansami zarządcy nieruchomości odpowiedzialnego za eksploatację kotłowni. Na tej podstawie mogą być planowane opłaty eksploatacyjne lub też operacje finansowe z wykorzystaniem okresowej nadwyżki kapitału, pochodzącej z różnicy pomiędzy wydatkami na zakup paliwa a opłatami za ogrzewanie.

The paper analyzed the natural gas sector in Ukraine for the period 2000 to 2018. This sector was affected by external factors, such as the crisis which began in late 2008/2009, as well as internal factors, including the situation in Ukraine after 2013 (the Annexation of Crimea). A comparative analysis was also conducted of the natural gas sector in European Union countries and Ukraine – compared the specificity of natural gas consumption in 2018. The analysis (I) examined the demand for natural gas in Ukraine between 2000 and 2018; (II) described changes in sources to cover Ukraine’s gas needs with a particular emphasis on its own production; (III) pointed to the fundamental changes that have occurred in the natural gas supply routes to the Ukrainian sector in recent years; (IV) stressed the growing role of own production in balancing Ukraine’s gas needs; (V) described the role of Ukraine as a transit country for Russian gas to be delivered to EU countries (in recent years, the volume of natural gas transmitted via the Ukrainian transmission system has been around 90 bcm annually); and (VI) looked at the structure of natural gas consumption in the Ukrainian gas sector and how it has changed in recent years. Unlike EU countries, the growing role of own production in balancing Ukraine’s natural gas needs was emphasized, which is consistent with the strategy of the Ukrainian government. Also, attention was drawn to the threats that may significantly reduce the role of Ukraine as an important transit country. The paper also puts forward the most important parameters concerning the underground natural gas storage facilities in Ukraine which is one of the largest in Europe.

Elektrofiltry należą do najczęściej stosowanych w energetyce urządzeń odpylających. Do niedawna sądzono, że wszelkie turbulencje w komorze odpylacza prowadzą do obniżenia skuteczności jego pracy, stąd dążono do osiągnięcia równomiernego przepływu spalin wewnątrz elektrofiltru. Zastosowanie komputerowego modelowania procesu odpylania w elektrofiltrze radykalnie zmieniło pogląd na rolę przepływu gazu w urządzeniu. Stwierdzono bowiem, że nierównomierne, odpowiednio ukształtowane przepływy spalin (tzw. przepływy skośne) prowadzą do poprawy skuteczności pracy odpylacza. W artykule dokonano przeglądu typów skośnych przepływów spalin stosowanych w elektrofiltrach oraz ich wpływu na skuteczność pracy urządzenia. Zaprezentowano wyniki własnych symulacji komputerowych, wykorzystujących prosty model obliczeniowy, obrazujące wpływ sposobu przepływu spalin na skuteczność odpylania w elektrofiltrze, ze szczególnym uwzględnieniem długości strefy. Wyniki badań wskazują, że zróżnicowanie prędkości spalin prowadzi do poprawy skuteczności odpylania szczególnie w przypadku krótkich stref w elektrofiltrze. W przypadku stref długich. maksymalna skuteczność odpylania jest osiągana, dla przyjętego dwuczęściowego modelu strefy odpylania, przy równomiernym przepływie spalin w urządzeniu.

In this paper, various repowering methods commonly employed in practice today are discussed. A particular emphasis is put on the hot wind-box repowering method, which is examined in greater detail. This method stands out for its simpler solution and lower investment costs compared to other repowering methods. Most research and analyses on repowering, taking into account the ecological problems and the possibilities of repowering existing old steam cycle power plants, have focused on the effect of repowering on thermodynamic parameters and emission reduction․ However, there are still many important questions that remain open and unexplored when it comes to analyze the selection of the right technology of the repowering and the right gas turbine for such a combined cycle power plant. For that purpose, based on the oxygen fraction in the gas turbine exhaust gases, nine different gas turbine models were tested for a 200 MW steam cycle power plant model. Calculations were carried out using the GateCycle modelling program. As a result of investigations, a GE Energy Oil & Gas MS9001E SC (GTW 2009 ‒ with 123 MW power) gas turbine was selected as the best one for such a combina-tion, in which case the increase of total net power output by 97.69% and the improvement of efficiency by 6.67% were registered, compared to the results before repowering, while carbon dioxide emissions were decreased by 0.29% per meg-awatt electrical power generated. The conducted research underscores the importance of selecting the right gas turbine for such a gas-steam system.

Energy security is one of the most frequently analysed phenomena in the energy markets. Great variety of scientifc efforts should have indicated clear definition of the phenomenon. However, those studies highlighted more than 80 different definitions of what energy security really is. Due to the fact, that energy security is analyzed by different scientific disciplines, studies have provided a comperehensive reflection on the phenomenon.

The main objective of this paper is of the theoretical nature and focuses on showing energy security externalities. Author delivers an integrative review focusing on existing literature referring to the analyzed phenomena. Energy security is though studied only from the perspective of economics therefore interdisciplinary studies are out of the study scope. The reason for such scientific procedure stem from a belief that each discipline approach is different in terms of concepts, research methods and though results that are obtained. Therefore without undermining high value of interdisciplinary approaches to energy security, author decided to concentrate solely on economic perspective, which in energy security studies seems to be underestimated. Such approach in author’s belief helps achieve theoretical clarity of the below given analysis.

Presented paper is of the theoretical nature and focuses on showing energy security externalities. Critical literature review shows the literature mainstream in which energy security externalities are

Underground gas storage facilities play an important part in the maintenance of balance between the constantly imported raw material and variable gas demand in the discussed part of Europe. They also allow for more the efficient operation of businesses which exploit this raw material in this part of Europe and operators of power lines.

The following issues will be discussed in the article: types, capacity, location and variability of the filling level of underground gas storage facilities in Poland, the Czech Republic, Hungary, and Slovakia; similarities and differences in the policy of natural gas storage between individual Visegrad Group countries; the influence of these differences on the situation in the gas market; the influence of the planned further reconstruction of the natural gas storage facilities system on the energy security of individual countries which belong to the Visegrad Group.

Concern for UGSF is one of the conditions of expansion of transmission pipelines to the north and south, increase of LNG import within the Visegrad Group, or the creation of a gas hub in Poland – initiatives aimed at, among others, securing the continuity of supplies to domestic users.

However, the current and planned investments indirectly indicate that in the policies of the governments of the Visegrad Group countries, UGSF are supposed to soon play a much smaller role than many researchers would expect. An intensive expansion of UGSF is very unlikely. The scale of the state’s effect on the role of storage facilities in supplying gas to users depends on the level of the state’s control over the companies managing UGSF.

The paper presents a thermodynamic analysis of the removal of an inert gas from the tank using the vapor of liquefied petroleum gas cargo (called cargo tank gassing-up operation). For this purpose a thermodynamic model was created which considers two extreme cases of this process. The first is ‘piston pushing’ of inert gas using liquefied petroleum gas vapour. The second case is the complete mixing of both gases and removal the mixture from the tank to the atmosphere until desired concentration or amount of liquefied petroleum gas cargo in the tank is reached. On the example of nitrogen as inert gas and ethylene as a cargo, by thermodynamic analysis an attempt was made to determine the technical parameters of the process, i.e., pressure in the tank, temperature, time at which the operation would be carried out in an optimal way, minimizing the loss of cargo used for gassingup. Calculations made it possible to determine the amount of ethylene used to complete the operation and its loss incurred as a result of total mixing of both gases.

The analysis of natural hazards, including gas-geodynamic phenomena, requires study of the basic physical processes that take place at each stage of an event. This paper focuses on analysing the transport of fragmented rock material during rock and gas outbursts. Our theoretical considerations and experiments have allowed us to specify and verify the significant forces acting on fragmented rock during its transport, thus determining the speed of grains of each grain class in the stream of expanding gas. The above study may serve as a preface to a wide-ranging quantitative and qualitative energy analysis of the movement of material ejected during Gas-geodynamic phenomena.