Search results

Filters

  • Journals
  • Authors
  • Keywords
  • Date
  • Type

Search results

Number of results: 5
items per page: 25 50 75
Sort by:
Download PDF Download RIS Download Bibtex

Abstract

The article presents an experimental investigation of the rheological properties of carbomer microgels. All of the tested fluids were made up from commercial polyacrylic acid, Carbopol Ultrez 30. In total, eighteen microgels were prepared, differing in concentration; 0.2, 0.4 and 0.6 wt%, with six levels of neutralisation for pH from 4.0 to 9.0. Based on the experimental flow curves it was found that all tested microgels are yield stress shear-thinning fluids. Therefore, the Herschel–Bulkley model was used and its rheological parameters were determined. It was found that both the concentration and the pH value significantly affected the yield stress. As the Carbopol concentration increased, the yield point also increased. With the increasing value of pH, the yield stress first increased until a certain maximum level and then decreased. The maximum values of yield stress were obtained for pH = 6 to 7, depending on polymer concentration. It was also found that flow curves of the tested microgels could be described using one universal master curve, thus they have common rheological behaviour.

Go to article

Authors and Affiliations

Anna Story
Grzegorz Story
Zdzisław Jaworski
Download PDF Download RIS Download Bibtex

Abstract

The study of the mechanical properties comprised fracture surface examination, texture and microstructure observations of copper samples, which were cold rolled, beginning from the recrystallized state or initially deformed by Equal-Channel Angular Pressing (ECAP) up to equivalent deformation E= 2.7. In cold rolled recrystallized copper, intensive shear band formation on the sample scale as well as on micro-scale was observed; shear bands in cold rolled copper, initially ECAP processed, were difficult to observe. Higher ultimate strength and greater elongation were measured in tensiled samples, cut out in RD direction of rolled to z= 96% copper sheet and preliminarily ECAP processed samples; strain marks on the lateral surface of such a sample in the neck region demonstrated the grain size diameter lower than I μm. Fracture surface observation of ruptured sheet samples of recrystallized copper has shown that it is possible to explain the lower elongation as a result of localised deformation in shear bands. In both cold rolled sheets, texture with { 112 }<11-1> ideal orientation was observed, although in preliminarily ECAP processed copper the dispersion of crystal orientation around the ideal orientation was smaller.
Go to article

Authors and Affiliations

Jan Kuśnierz
Joanna Bogucka
Download PDF Download RIS Download Bibtex

Abstract

One of the fundamental problems in evolutionary sciences is the direction of evolution at different levels of matter organization. According to traditional teleological interpretations, the evolving systems should develop toward a final state—a goal. However, in most cases such a goal is not determinable—scientists do not know it. However, they can reveal a general tendency or a series of changes in time: a teleonomy or a directness based mainly upon an internal pattern of the evolving system although modified also by external influences. Teleonomical processes are responsible for all evolutionary processes including transitions from one level of organization to another.

Go to article

Authors and Affiliations

Leszek Żuk
Download PDF Download RIS Download Bibtex

Abstract

Turkowski refers to Michał Przeperski’s much-read biography of Mieczysław F. Rakowski, which constitutes interesting literature not only for those interested in the political history of the Polish People’s Republic, but also for those researching social processes in post-war Poland. In particular, Turkowski ascertains that one can discover numerous valuable observations concerning the issue of social advancement in this biography, observations that question the durability of the heritage of the system of real socialism in this respect.
Go to article

Authors and Affiliations

Andrzej Turkowski
1
ORCID: ORCID

  1. Uniwersytet Warszawski
Download PDF Download RIS Download Bibtex

Abstract

The article is devoted to the late Zygmunt Bauman (d. January 2017), a scholar who made an enormous impact on world humanities at the turn of the twentieth century. It briefly presents Bauman’s life and a number of the best known concepts from his works. The author first discusses Bauman’s attitude toward Marxist theory and explains his revision of it. He then introduces the main ideas of Bauman work Modernity and the Holocaust. The article ends with a review of Bauman’s reflections on globalisation and a discussion of his thesis concerning the crisis of the nation state.

Go to article

Authors and Affiliations

Jacek Raciborski

This page uses 'cookies'. Learn more