Temat: compression - Prolib Integro

Skocz do pozycji: 1.

Tytuł:: Compressed arsenolite As4O6 and its helium clathrate As4O6·2He
Autorzy:: Hanfland, Michael
Piechota, Jacek
Gładysiak, Andrzej
Zachara, Janusz
Dranka, Maciej
Katrusiak, Andrzej
Guńka, Piotr
Dziubek, Kamil F.
Wydawca:: American Chemical Society
Opis:: Jacek Piechota
Crystal structure of arsenolite, the cubic polymorph of arsenic(III) oxide, has been determined by single crystal X-ray diffraction up to 30 GPa. The bulk of the crystal is monotonically compressed with no detectable anomalies, to 60% of the initial volume at 30 GPa. In the structure the most compressed are As···As contacts which contrasts with increased intramolecular As···As distance in the deformed molecule. The ratio between As···As inter- and intramolecular distances decreases from 1.47 at 0.1 MPa 10 to 1.03 at 30 GPa. The As4O6 molecules are deformed to become more tetrahedron-like. Pressure above 3 GPa favours the formation of As4O6·2He inclusion compound in the surface layer increasingly deeper with pressure. The experimental As4O6 crystal compression has been compared with various theoretical models within the DFT framework. According to band-structure calculations the arsenolite band gap falls from 4.2 eV at ambient pressure to 2.7 eV at 27.8 GPa.
National Science Centre, Polish Ministry of Science and Higher Education
Dostawca treści:: Repozytorium Centrum Otwartej Nauki

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Skocz do pozycji: 2.

Tytuł:: Peculiar traits of wood in a leaning stem of Scots pine (Pinus sylvestris L.)
Autorzy:: Tulik, Mirela
Jasińska, Aleksandra
Wydawca:: The Committee on Forestry Sciences and Wood Technology of the Polish Academy of Sciences and the Forest Research Institute in Sekocin Stary
Opis:: The paper analyses biometrical and anatomical traits of wood in a leaning stem of pine trees. For study purpose, five pine trees (Pinus sylvestris L.) with a visibly leaning stem were chosen. Wood samples were taken at three different stem heights, that is, below the stem curvature, at the curvature and above the curvature. Microscopic specimens were prepared and used for the following measurements: annual rings width, tracheids diameter and tracheids wall thickness. The measurements were performed for wood located on the lower side of the leaning stem and on the opposite side. Cytochemical staining was performed to identify the occurrence of laricinan. The results showed tracheids with a rounded shape and thick cell walls, helical cavities and intercellular spaces in wood located at curvature height on the lower side of the leaning stem. These traits indicate a severe compression wood that allowed pine trees to change their stem position in relation to the vector of gravity.
Dostawca treści:: Repozytorium Centrum Otwartej Nauki

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Skocz do pozycji: 3.

Tytuł:: Evaluation of expansivity of Neogene clays and glacial tills from cental Poland (Warszawa area) on the basis of suction tests
Autorzy:: Wójcik, Emilia
Izdebska-Mucha, Dorota
Wydawca:: Polish Geological Institute - National Research Institute
Opis:: This paper presents the characteristics of the expansivity and quantitative prediction of heave of clay soils from Poland based on suction testing. Eleven Neogene clays and six glacial tills, differing in genesis and plasticity, were analysed to identify the expansive potential using eight empirical methods. The laboratory studies included measurements of soil-water characteristic curves and soil index properties. Data from water content, volume and suction measurements served to determine the suction compression index Ch and the suction-water content index delta h/delta w of the soils examined. The values of these indices are clearly dependent on the clay fraction content in tested soils. Compared with glacial tills, Neogene clays are expected to exhibit greater changes in volume due to changes in soil suction. Comparative results of the evaluation of expansivity suggest that the chosen classification methodologies provided consistent expansion ratings for glacial tills, while the values for Neogene clays vary from low to very high. The lowest expansivity classes have been obtained from evaluation based on soil suction. The McKeen (1992) method has been adopted for calculations of the potential field heave of Neogene clays and glacial tills. In order to provide a rational estimation of expansive soil behavior, specialists should take into consideration the specific site and design features.
Dostawca treści:: Repozytorium Centrum Otwartej Nauki

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Skocz do pozycji: 4.

Tytuł:: Parametric study of geometry effect on response to applied loadings of metallic honeycomb structures by virtual testing of mesoscale models
Autorzy:: Pietras, Daniel
Sadowski, Tomasz
Wydawca:: Polish Academy of Sciences, Committee of Metallurgy, Institute of Metallurgy and Materials Science
Cytata wydawnicza:: Pietras, D., Sadowski, T. (2018) Parametric Study of Geometry Effect on Response to Applied Loadings of Metallic Honeycomb Structures by Virtual Testing of Mesoscale Models. Archives of Metallurgy and Materials Vol. 63, iss. 2 pp. 953-961
Opis:: In this paper were conducted virtual tests to assess the impact of geometry changes on the response of metallic hexagonal honeycomb structures to applied loadings. The lateral compressive stress state was taken into consideration. The material properties used to build numerical models were assessed in laboratory tests of aluminum alloy 7075. The modeling at the mesoscale level allow to a comprehensive study of honeycomb internal structure. The changes of honeycomb geometry elements such as fillets radius of the cell edges in the vicinity of hexagonal vertexes, wall thickness were considered. The computations were conducted by using the finite element method with the application of the ABAQUS finite element method environment. Elaborated numerical models allowed to demonstrate the sensitivity of honeycomb structures damage process response to geometry element changes. They are the proper tools to perform the optimization of the honeycomb structures. They will be also helpful in designing the process of modern construction build-up of the considered composite constituents in various branches of industry. Moreover, the obtained results can be used as a guide for engineers. Conducted virtual tests lead to the conclusion that simplification of the models of internal honeycomb structure which has become commonplace among both engineers and scientists can lead to inaccurate results.
The European Union’s Horizon 2020 research and innovation program under the Marie Skłodowska-Curie grant agreement No. 665778
Dostawca treści:: Repozytorium Centrum Otwartej Nauki

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