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Number of results: 29
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Abstract

Traditional mass balance measurements by stake readings and snow surveying have been conducted annually since 1996 on the Waldemar Glacier (= Waldemarbreen) in northwest Spitsbergen, Svalbard. Several indirect methods were also used for estimating its mass balance. These methods were divided into two major groups: climatological and geodetic. A comparison of the latest map (2000) with that of 1978 and climatological records enable us to calculate the change in the mass balance of Waldemarbreen over 34 years. These methods include air temperature and degree-day (PDD) models. The average mass balance of Waldemarbreen, computed by climatological methods, was -0.42 m a-1 of water equivalent (w.e.) for the period 1970-2004, and -0.51 m w.e. for 1996-2004. These balances were compared with the glaciological balance for the period 1996-2004, -0.53 m w.e.. The mass balance was also computed using geodetic method, giving -0.52 m of w.e. from 1978 to 2000. It is suggested that, from these results, the approach used for Waldemarbreen might be also useful for estimation the mass balances of other small Svalbard glaciers which terminate on land.
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Abstract

On the basis of a year-long series of actinometric measurements performed in the vicinity of Polish Polar Station at Hornsund, this paper presents the characteristic of the value of solar radiation incoming at the active surface, of absorbed and net radiation. The maximum intensity of the direct solar radiation was 822 Wm-2, the annual sum total of total radiation was 2611 MJm-2, whereas the mean yearly albedo was 59%. The zero-crossing of the 24-hour sums of the net radiation towards negative values occurred at the turn of September and October.
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Abstract

In recent years, changes have been made in the structure of primary energy use in the European Union In addition, a reduction in the use of primary energy has also been observed. According to the forecasts of the International Energy Agency, the European energy market will be subject to further changes in the perspective of 2040. These may include the reduction of the energy consumption and the change in the structure of the energy balance as a result pro-ecological activities. Natural gas will be the only fossil energy carrier whose role in covering the energy demand will not change. Along with the changes taking place in the European energy market, global changes can also be observed. The EU Member States will continue to strive to diversify natural gas supplies. One of the main elements of diversification of natural gas supplies is the use of LNG regasification terminals. The reasons for that include the increasing production of natural gas, particularly in the case of unconventional deposits, the ongoing development of liquefaction terminals, and, as a consequence, an increase in the LNG supply in the global market. The article presents the utilization of regasification terminals in the EU Member States and plans for the development of LNG terminals. Europe has the opportunity to import natural gas through LNG terminals. However, until now, these have been used to a limited extent. This may indicate that in addition to diversification tasks, terminals can act as a safeguard against interruptions in gas supplies.
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Abstract

All local government units in Poland have been analysed regarding their consolidated debt. The consolidated debt was compared with the budget debt which is subject to monitoring and statutory restrictions. The scale of extra-budgetary debt has been revealed as recorded in the balance sheet of a local government unit, a parent entity. In practice, the consolidated balance sheet and debt presented in it are not subject to debates and analyses. Local governments refrain from auditing and publicising of the consolidated balance sheet. The article describes the risks related to unlimited local government debt.
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Abstract

The large variability and unpredictability of energy production from photovoltaic power microinstallations results from the dependence on the current weather conditions. These conditions depend on a number of factors and are variable over the time. Despite this specificity, photovoltaic micro-installations are becoming more and more popular in the world and in Poland. This is mainly due to the fact that the generation of energy from renewable sources has numerous advantages, the energy is free, renewable in time and ecological, and its production on its own gives partial independence from energy supplies from the power grid. In addition, the observed significant prices decrease of solar modules has further accelerated the development of the use of this energy source. Concern for this method of energy production among households has increased significantly in Poland after introducing the prosumer in the legal framework and the use of administrative and financial support. The implemented prosumer mechanisms allowed, for example, the net balancing of the energy consumed and produced by the micro-installation through storage in the power grid. The article describes the problem of balancing sources using solar energy, based on micro-installation used in the household (the so-called prosumer installation). The conducted analyses compared the load profile of a typical household and the energy generation profile from a photovoltaic installation, determining the real balancing formation level of such a system.
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Abstract

Knowledge of the temperature distribution in subsurface layers of the ground is important in the design, modelling and exploitation of ground heat exchangers. In this work a mathematical model of heat transfer in the ground is presented. The model is based on the solution of the equation of transient heat transfer in a semi-infinite medium. In the boundary condition on the surface of the ground radiation fluxes (short- and long-wave), convective heat flux and evaporative heat flux are taken into account. Based on the developed model, calculations were carried out to determine the impact of climatic conditions and the physical properties of the ground on the parameters of the Carslaw-Jeager equation. Example results of calculated yearly courses of the daily average temperature of the surface of the ground and the amount of particular heat fluxes on the ground surface are presented. The compatibility of ground temperature measurements at different depths with the results obtained from the Carslaw–Jaeger equation is evaluated. It was found that the temperature distribution in the ground and its variability in time can be calculated with good accuracy.
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Abstract

An attempt to summarize the primary iron raw materials and steel market’s hundred years history as well as influence of economic indicators on the iron ore deposit qualification for extraction has been undertaken in the paper. Steel products are crucial to the world economy, and their production has a major impact on the environment. The main factor is the huge scale of the production and growth rate, unprecedented among minerals. Iron ore and concentrates production has increased more than thirty times over the past century, and the geological resource base at the current level of consumption has provided almost 250 years of sufficiency. There have been tremendous changes in the world geography of the ore and steel industry. The iron ore mining industry is the driver of other economic activities (land transport, freight, metallurgy) and involves huge capital and human resources. The consumption of iron raw materials is also considered as an important indicator of the countries development and current or even future economic situation. Population growth remains one of the key stimulating factors. The prices of ore and iron concentrates depend on the quality of the raw material, delivery conditions, market balance and the weight of the ordered cargo. They are usually the subject of negotiations. In the past, they were long-term contracts, while short-term (yearly, quarterly) and current spot transactions are now significant. The prices of ores and concentrates in relation to steel prices are showing a strong correlation. The average iron content of the reserves has been reduced in the largest producers in the 21st century, however it does not translate into the quality of mining output. Exploitation of the richer parts of the mineral deposit is usually carried out. The high content of iron in the output is a response to the technological requirements of the metallurgy where the blast furnace charge should contain at least 56% Fe and 5–8% FeO. The current surplus of geological-mining supply (large resource base) justifies that a mineral deposit choice, destined for excavation, is economic profit maximization as well as social and environmental considerations.
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Abstract

The goal of this article is to discuss dynamics hindering women's career in managerial roles of Polish comprehensive universities. Although female academics outnumber their male peers, they remain underrepresented in the management at universities. In the last 30 years, only 2 women held a position of rector. In this article, we analyse the reasons for this phenomenon on the basis of qualitative research performed with the use of individual in-depth interviews, preceded by the analysis of career advancement of individual women. The research has been carried out on a group of 15 women, which currently occupy position of vice-rector or have had position of rector in the past. The results of the analysis show that occupying a position of vice-rector is a key factor determining the chance to obtain a position of rector. This stage of the career helps to consolidate the chosen professional role in the organisation (3 main roles were recognised: expert, researcher and activist). Depending on the type, these roles give greater or lesser opportunities for self-identification in the position of a leader, for adapting to collegial culture of university and as a consequence becoming a rector.
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Abstract

Many precision devices, especially measuring devices, must maintain their technical parameters in variable ambient conditions, particularly at varying temperatures. Examples of such devices may be super precise balances that must keep stability and accuracy of the readings in varying ambient temperatures. Due to that fact, there is a problem of measuring the impact of temperature changes, mainly on geometrical dimensions of fundamental constructional elements of these devices. In the paper a new system for measuring micro-displacements of chosen points of a constructional element of balance with a resolution of single nanometres and accuracy at a level of fractions of micrometres has been proposed.
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Abstract

Energy from different sources is fundamental to the economy of each country. Bearing in mind the limited reserves of non-renewable energy sources and the fact that their production from new deposits is becoming less economically viable, attention is paid to alternative energy sources, particularly those that are readily available or require no substantial financial investment. One possible solution may be to generate hydrogen, which will then be used for heat (energy) production using other methods. At the same time, these processes will be characterized by low emission levels compared to conventional energy sources. In recent years, more and more emphasis has been placed on the use of clean energy from renewable sources. New, more technically and economically efficient technologies are being developed. The energy use worldwide comes mostly from fossil fuel processing. It can be observed that the share of RES in global production is growing every year. At the end of the 1990s, the share of renewable energy sources was at 6–7%. Global trends indicate the increasing demand for renewable energy due to its form. Global hydrogen resources are practically inexhaustible, but the problem is its availability in molecular form. The article analyzed the use of hydrogen as a fuel. The basic problem is the inexpensive and easy extraction of hydrogen from its compounds; attention has been paid to water, which can easily be electrolytically decomposed to produce oxygen and hydrogen. Hydrogen generated by electrolysis can be stored, but due to its physicochemical properties, it is a costly process; therefore, a decision was made that it is better to store it with natural gas or use it for further reaction. In addition, hydrogen can be used as a substrate for binding and converting the increasingly problematic carbon dioxide, thus reducing its content in the atmosphere.
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Abstract

The article is focused onthe energetical balance of a technical system for the conversion of crushed tyres by pyrolysis. Process temperatures were set in the range from 500 to 650°C. Mass input of the material was 30 kg per hour. The aim of the article is to answer the following questions as regards the individual products: Under which process conditions can the highest quality of the individual products related to energy be reached? How does the thermal efficiency of the system change in reaction to various conditions of the process? On the basis of the experimental measurements and calculations, apart from other things, it was discovered that the pyrolysis liquid reaches the highest energetic value, i.e. 42.7 MJ.kg-1, out of all the individual products of the pyrolysis process. Generated pyrolysis gas disposes of the highest lower calorific value 37.1 MJ.kg-1 and the pyrolysis coke disposes of the maximum 30.9 MJ kg-1. From the energetic balance, the thermal efficiency of the experimental unit under the stated operational modes ranging from about 52 % to 56 % has been estimated. Individual findings are elaborated on detail in the article.
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Abstract

Balance, thermodynamic and mainly kinetic approaches using methods of process engineering enable to determine conditions under which iron technology can actually work in limiting technological states, at the lowest reachable fuel consumption (reducing factor) and the highest reachable productivity accordingly. Kinetic simulation can be also used for variant prognostic calculations. The paper deals with thermodynamics and kinetics of iron making process. It presents a kinetic model of iron oxide reduction in a low temperature area. In the experimental part it deals with testing of iron ore feedstock properties. The theoretical and practical limits determined by heat conditions, feedstock reducibility and kinetics of processes are calculated.
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Abstract

Compared to other European countries, Poland has scarce drinking water resources and exhibits significant variation in annual runoff. On the other hand, the geothermal water resources present in sedimentary/structural basins, mostly in the Polish Lowlands and the Podhale geothermal system, not only provide a valuable source of renewable energy, which is utilized, although only to a limited extent, but can also be used for many other purposes. The paper presents the results of studies related to the desalination of low dissolved mineral content geothermal waters from the Bańska IG-1 well using a dual hybrid system based on ultrafiltration and reverse osmosis. The desalination of geothermal waters may be considered a possible solution leading to the decentralization of drinking water supply. In many cases, using cooled waters for drinking purposes may be considered an alternative method of disposing of them, in particular for open drain arrangements, i.e. where cooled water is dumped into surface waters.
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Abstract

The paper presents abilities and advantages following from the use of the harmonicbalance method for analysis of steady state of a multiphase system with switching devices on example of a matrix converter. Switching elements are modelled as resistances with step-wise variable parameters, what allows to describe the converter by a linear infinite set of equations. The analysis in frequency domain is presented on example of the one-periodic control strategy. External systems were also added using the Thevenin method approach. The numerical calculation results of a linear equations set were verified by the variable structure method in a time domain and the numerical convergence was confirmed. Furthermore, the exemplary complex system was analysed using the cascade method and current waveforms were obtained.
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Abstract

Effective use of energy in various branches of economy is one of world trends in development of power engineering. Relevant energy consumption occurs during exploitation of buildings, so there is still potential to diminish it as far as heating, ventilation, and air conditioning are concerned. Particularly in summer season, the choice of respective roofing colour can play a decisive role for the heat flux transferred to the inside of the object. Decrease of heat flux causes a lower heat burden to the building and lower power consumption by the air conditioning systems. In winter, on the contrary, heat flux transferred to building’s interior should be higher, as a result, demand of energy for heating will be lower. However, calculations of the heat flux require that energy balance must be made for the object. Unfortunately, not all producers of roofing covers inform about the values of reflectivity and thermal emissivity of their products, which is, in turn, necessary for calculations. In the present paper, research methodology elaborated by authors is proposed for determination of thermal emissivity of roofing covers. The paper presents test stand, methodology, and research results for roofing paper in blue colour (as an example) for which the thermal emissivity is an unknown parameter.
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Abstract

The paper discusses the water resources of the Krężniczanka River catchment. The catchment with an area of 224.9 km2 is located south-west of Lublin. The characteristics of the groundwaters and runoff were determined based on hydrological and hydrogeological materials of the Department of Hydrology of the Maria Curie-Skłodowska University (UMCS). Mean runoff in the period from 2010 to 2016 amounted to 125.7 mm, precipitation 629.4 mm, and evapotranspi-ration 503.7 mm. A strong relationship was determined between the rhythm of runoff and ground-water level fluctuations. The contribution of groundwater supply in total runoff equalled 81.5%.
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Abstract

In many systems of engineering interest the moment transformation of population balance is applied. One of the methods to solve the transformed population balance equations is the quadrature method of moments. It is based on the approximation of the density function in the source term by the Gaussian quadrature so that it preserves the moments of the original distribution. In this work we propose another method to be applied to the multivariate population problem in chemical engineering, namely a Gaussian cubature (GC) technique that applies linear programming for the approximation of the multivariate distribution. Examples of the application of the Gaussian cubature (GC) are presented for four processes typical for chemical engineering applications. The first and second ones are devoted to crystallization modeling with direction-dependent two-dimensional and three-dimensional growth rates, the third one represents drop dispersion accompanied by mass transfer in liquid-liquid dispersions and finally the fourth case regards the aggregation and sintering of particle populations.
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Abstract

The main topic of this study is the mathematical modelling of bubble size distributions in an aerated stirred tank using the population balance method. The air-water system consisted of a fully baffled vessel with a diameter of 0.29 m, which was equipped with a six-bladed Rushton turbine. The secondary phase was introduced through a ring sparger situated under the impeller. Calculations were performed with the CFD software CFX 14.5. The turbulent quantities were predicted using the standard k-ε turbulence model. Coalescence and breakup of bubbles were modelled using the MUSIG method with 24 bubble size groups. For the bubble size distribution modelling, the breakup model by Luo and Svendsen (1996) typically has been used in the past. However, this breakup model was thoroughly reviewed and its practical applicability was questioned. Therefore, three different breakup models by Martínez-Bazán et al. (1999a, b), Lehr et al. (2002) and Alopaeus et al. (2002) were implemented in the CFD solver and applied to the system. The resulting Sauter mean diameters and local bubble size distributions were compared with experimental data.
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Abstract

The work is a part of research into the reduction of energy consumption in the production of EPSthrough the modernization of technological equipment used. This paper presents the results of research and analysis of heat transfer process between the water vapor that was provided to machine, the mold, the product and the environment. The paper shows the calculation of the heat balance of the production cycle for two types of mold: standard and modernized. The performance tests used an infrared imaging camera. The results were used to develop a computer image analysis and statistical analysis. This paper presents the main stages of the production process and the construction of technological equipment used, changing the mold surface temperature field during the production cycle and the structure of the heat balance for the mold and its instrumentation. It has been shown that the modernization of construction of technological equipment has reduced the temperature field and as a consequence of decreased of demand for process steam production cycle.
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Abstract

The paper investigates a significant influence of transients on steady states in a matrix converter with the one-periodic control strategy. Proposed controller can be used as an interconnection device within a power system for a power flow control. However, the presence of inductances in external systems has the significant influence on steady state of a matrix converter operation. The special current injection method has been developed to ensure a proper operation of a matrix converter. Presented analysis of steady states is carried out in a frequency domain using the harmonic balance method. Obtained numerical results, which are confirmed by a time domain analysis, prove the effectiveness of the proposed method.
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Abstract

During studying and mathematical description of the trends of urbanized territories development as ecological and town-planning systems there were several vague similarities founded between its major parameters change periodicity and other physical values, having undulatory nature. Obtained counterparts had predetermined interest for search of fundamental basics of urbanization. It turned out that all laws of Nature has the same basis – power permanence rule. This law is known in philosophy as principle of «change of unchangeable», in ecology – as a law of ecosystem self-regulation, in accordance to which at conditions of insufficient occupancy of the territory the population amount growths, and at conditions of over-occupancy it decreases. According to research, also development attributable to the dynamics of urbanized territories is noticeable, in which all the four types of physical interactions are expressed to a certain degree. These and other results of research have allowed to articulate the main principles of ecological space «urban physics» content, which have proven to be coordinated with the postulates of new single field physics (Bishkek version). The above-mentioned have allowed to lay down the theoretical foundation for an occurrence of a new branch in the science of townplanning i.e. wave urbanistics, as a science of management by unduly processes of territories development in order to provide a conditions of their sustainable development.
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Abstract

The paper presents the results of numerical computations performed for the furnace chamber waterwalls of a supercritical boiler with a steam output of 2400 × 103 kg/h. A model of distributed parameters is proposed for the waterwall operation simulation. It is based on the solution of equations describing the mass, momentum and energy conservation laws. The aim of the calculations was to determine the distribution of enthalpy, mass flow and fluid pressure in tubes. The balance equations can be brought to a form where on the left-hand side space derivatives, and on the right-hand side – time derivatives are obtained. The time derivatives on the right-hand side were replaced with backward difference quotients. This system of ordinary differential equations was solved using the Runge-Kutta method. The calculation also takes account of the variable thermal load of the chamber along its height. This thermal load distribution is known from the calculations of the heat exchange in the combustion chamber. The calculations were carried out with the zone method.
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Abstract

To minimize oxides of nitrogen (NOx) emission, maximize boiler combustion efficiency, achieve safe and reliable burner combustion, it is crucial to master global boiler and at-the-burner control of fuel and air flows. Non-uniform pulverized fuel (PF) and air flows to burners reduce flame stability and pose risk to boiler safety by risk of reverse flue gas and fuel flow into burners. This paper presents integrated techniques implemented at pilot ESKOM power plants for the determination of global boiler air/flue gas distribution, wind-box air distribution and measures for making uniform the flow being delivered to burners within a wind-box system. This is achieved by Process Flow Modelling, at-the-burner static pressure measurements and CFD characterization. Global boiler mass and energy balances combined with validated site measurements are used in an integrated approach to calculate the total (stoichiometric + excess) air mass flow rate required to burn the coal quality being fired, determine the actual quantity of air that flows through the burners and the furnace ingress air. CFD analysis and use of at-the-burner static, total pressure and temperature measurements are utilized in a 2-pronged approach to determine root-causes for burner fires and to evaluate secondary air distribution between burners.
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