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Lukasz Jarosinski, Andrzej Rybak, Karolina Gaska, Grzegorz Kmita, Renata Porebska and Czeslaw Kapusta

Abstract

Efficient heat dissipation from modern electronic devices is a key issue for their proper performance. An important role in the assembly of electronic devices is played by polymers, due to their simple application and easiness of processing. The thermal conductivity of pure polymers is relatively low and addition of thermally conductive particles into polymer matrix is the method to enhance the overall thermal conductivity of the composite. The aim of the presented work is to examine a possibility of increasing the thermal conductivity of the filled epoxy resin systems, applicable for electrical insulation, by the use of composites filled with graphene nanoplatelets. It is remarkable that the addition of only 4 wt.% of graphene could lead to 132 % increase in thermal conductivity. In this study, several new aspects of graphene composites such as sedimentation effects or temperature dependence of thermal conductivity have been presented. The thermal conductivity results were also compared with the newest model. The obtained results show potential for application of the graphene nanocomposites for electrical insulation with enhanced thermal conductivity. This paper also presents and discusses the unique temperature dependencies of thermal conductivity in a wide temperature range, significant for full understanding thermal transport mechanisms.

Open access

Krzysztof Grudzień, Zbigniew Chaniecki, Bartosz Matusiak, Andrzej Romanowski, Grzegorz Rybak and Dominik Sankowski

Abstract

Measuring changes of bulk materials concentration during gravitational flow, a silo emptying is essential information for the assessment of the behaviour and condition of the material during the emptying of the silo. Parameters obtained during this process are important both in terms of process economics and safety, are the basis for monitoring and diagnostics of the process. Affect the current process, but primarily are the result of their filling the silo, and the process of storing the material. Previous studies, conducted by a team of authors, the laboratory-scale silos and numerical calculations and simulations of its increase, helped build the ECT sensor on a large scale. Results related to the change of scale of the sensor and the actual measurements will be discussed in the article. Proposed by the authors of the paper, the method of visualization, performed in the measuring process, helps to ask about the process and suggests a methodology for dealing with the material stored in the silo.

Open access

Zbigniew Chaniecki, Krzysztof Grudzień, Tomasz Jaworski, Grzegorz Rybak, Andrzej Romanowski and Dominik Sankowski

Abstract

The paper presents results of the scale-up silo flow investigation in based on accelerometer signal analysis and Wi-Fi transmission, performed in distributed laboratory environment. Prepared, by the authors, a set of 8 accelerometers allows to measure a three-dimensional acceleration vector. The accelerometers were located outside silo, on its perimeter. The accelerometers signal changes allowed to analyze dynamic behavior of solid (vibrations/pulsations) at silo wall during discharging process. These dynamic effects are caused by stick-slip friction between the wall and the granular material. Information about the material pulsations and vibrations is crucial for monitoring the interaction between silo construction and particle during flow. Additionally such spatial position of accelerometers sensor allowed to collect information about nonsymmetrical flow inside silo.

Open access

Andrzej Konon, Szymon Ostrowski, Barbara Rybak-Ostrowska, Mirosław Ludwiniak, Michał Śmigielski, Michał Wyglądała, Joanna Uroda, Sebastian Kowalczyk, Radosław Mieszkowski and Agnieszka Kłopotowska

Abstract

A newly recognized Mnin restraining stepover is identified in the Permo-Mesozoic cover of the western part of the Late Palaeozoic Holy Cross Mountains Fold Belt (Poland), within a fault pattern consisting of dextral strike-slip faults. The formation of a large contractional structure at the Late Cretaceous – Cenozoic transition displays the significant role of strike-slip faulting along the western border of the Teisseyre-Tornquist Zone, in the foreland of the Polish part of the Carpathian Orogen. Theoretical relationships between the maximum fault offsets/ mean step length, as well as between the maximum fault offsets/mean step width allowed the estimation of the values of possible offsets along the Snochowice and Mieczyn faults forming the Mnin stepover. The estimated values suggest displacements of as much as several tens of kilometres. The observed offset along the Tokarnia Fault and theoretical calculations suggest that the strike-slip faults west of the Late Palaeozoic Holy Cross Mountains Fold Belt belong to a large strike-slip fault system.

We postulate that the observed significant refraction of the faults forming the anastomosing fault pattern is related also to the interaction of the NW-SE-striking faults formed along the western border of the Teisseyre- Tornquist Zone and the reactivated WNW-ESE-striking faults belonging to the fault systems of the northern margin of the Tethys Ocean.

Open access

Lubomira Burchardt, František Hindák, Jiří Komárek, Horst Lange-Bertalot, Beata Messyasz, Marta Pikosz, Łukasz Wejnerowski, Emilia Jakubas, Andrzej Rybak and Maciej Gąbka

Abstract

Getting to know the response of different groups of aquatic organisms tested in altered thermal environments to environmental conditions makes it possible to understand processes of adaptation and limitation factors such as temperature and light. Field sites were located in three thermally abnormal lakes (cooling system of power plants), in eastern part of Wielkopolska region (western Poland): Pątnowskie, Wąsosko-Mikorzyńskie and Licheńskie. Water temperatures of these lakes do not fall below 10°C throughout the year, and the surface water temperature in spring is about 20˚C. In this study, we investigated the species structure of the spring phytoplankton community in a temperature gradient and analyzed diversity of periphyton collected from alien species (Vallisneria spiralis) and stones. 94 taxa belonging to 56 genera of algae (including phytoplankton and periphyton) were determined. The highest number of algae species were observed among Chlorophyta (49), Bacillariophyceae (34) and Cyanobacteria (6). In spite of important differences in temperature in the investigated lakes, taxonomic composition of phytoplankton was comparable. Thermophilic species: Glochidinium penardiforme and Cylindrospermopsis raciborskii were found in the species structure (blooms were not observed). The obtained data also showed that the biotic surface of Vallisneria spiralis was a better substrate for Bacillariophyceae colonization than stones. The examination in the spring season of these thermally altered lakes, indicated the taxonomic composition of phytoplankton typical for eutrophic reservoirs (not heated). There was no replacement of any phytoplankton groups which are characteristic for spring conditions, even if there were changes in the competition dynamics.