1,462 research outputs found
Running performance of an aerodynamic journal bearing with squeeze film effect
No full textResults of theoretical and experimental studies concerning the performance of an aerodynamic journal bearing which running is assisted by squeeze film ultrasonic levitation (SFUL) are presented in this paper. The SFUL mechanism not only can separate journal from the bearing at the start and stop phases of operation but also can significantly contribute to the dynamic stability of the bearing when it runs at speed. Computer calculations and validating experimental testing of a prototype device were carried out. It was found that that SFUL mechanism, when combined with aerodynamic lift, extends the threshold speed of bearing’s instability by almost four times comparing to that of a bearing operating without SFUL. Typically, the bearing running without SFUL became unstable at the speed of 300 rpm while with the SFUL the speed at which instability became apparent was 10,000 rpm (calculated result) or 13,200 (experimental result)
Peculiarities associated with testing polyetheretherketone (PEEK) in a model rolling contact
No full textCommonly used four-ball testing configuration when used to investigate rolling contact behavior of polyetheretherketone (PEEK) produced some unexpected peculiarities, namely direct contact between ceramic balls. Direct contact between lower three balls is normally not expected to take place when elastic materials (ferrous or ceramics) are tested. However, due to the viscoelastic nature of PEEK surface damage of the ceramic balls were observed leading to the production of wear debris which in turn facilitated premature failure of PEEK components of the assembly. It is postulated that caution is required when using the four-ball testing configuration to assess rolling contact performance of viscoelastic materials, such as engineering polymers.Gdansk University of Technology, Gdansk, Poland(Grant DS-2012)
Behavioral genetic study of time perspectives
No full textThe dataset contains the data collected within the GALTON study, which was a part of a research program entitled "In search for time perspective origins: Genetic and environmental bases of subjective attitudes towards time" funded by National Science Centre, Poland (2014/13/D/HS6/02951), awarded to Maciej Stolarski. Participants were 411 Polish same-sex twin pairs, reared together. The participants completed a set of measures including a 64-item version of the Zimbardo Time Perspective Inventory (ZTPI), the 50 item set of International Personality Item Pool Big Five Factor Markers (IPIP-BFM-50) questionnaire (Goldberg, 1992) in the Polish adaptation by Strus et al. (2017). Zygosity was diagnosed by the Polish version of the Questionnaire of Twins Physical Resemblance (QTPR; Oniszczenko & Rogucka, 1996). The predictive accuracy of the scale reaches 93.9% (96.2% for monozygotic and 90% for dizygotic pairs). In the case of a discrepancy between QTPR-based and self-reported zygosity, couples were excluded from the analyses. The ultimate sample comprised 393 same-sex twin pairs, reared together. Among them 135 were classified as monozygotic (MZ) and 258 as dizygotic (DZ) twins. MZ twins (88 females, 47 males) were aged between 15 and 48 years (M=24, SD=7.1) and DZ (189 females and 69 males) were between 15 and 57 years (M=21.9, SD=5.6).THIS DATASET IS ARCHIVED AT DANS/EASY, BUT NOT ACCESSIBLE HERE. TO VIEW A LIST OF FILES AND ACCESS THE FILES IN THIS DATASET CLICK ON THE DOI-LINK ABOV
Optimization of agricultural practices for crambe in Europe
No full textCrambe (Crambe abyssinica Hochst R.E. Fries) has recently attracted a renewed interest by the bio-based industry due to its high seed oil content (up to 57%), particularly erucic acid (up to 65% of total fatty acids), short growing cycle, and high drought tolerance. A field trial was conducted during four consecutive growing seasons (2016−19) in Greece, Poland, and Italy. The commercial crambe variety (Galactica) was sown in early, intermediate, and late sowing dates in spring at two seeding rates (LD: 100 seeds m−2, and HD: 200 seeds m−2) in a factorial design at each test location. Mean crambe seed yields exceeded 1.5 Mg DM ha-1 across all years and locations. Italy and Greece were the most productive sites, with average seed yields of 2.11 Mg DM ha-1 and 1.97 Mg DM ha-1, respectively. Oil yield, which was only determined in Italy and Poland, was about 30% greater in the southern environment (Italy). Nevertheless, 1000-seed weight was greater in Poland (6.49 g) than Italy (6.12 g), revealing that lower temperatures during seed filling resulted in heavier seeds. In conclusion, sowing date played a key role in crambe productivity, with the earliest sowing resulting in highest yields across all locations
Running characteristics of aerodynamic bearing with self-lifting capability at low rotational speed
No full textThis article has been made available through the Brunel Open Access Publishing Fund - Copyright @ 2011 Tadeusz Adam Stolarski.An aerodynamic journal bearing that is capable of self-generating squeeze-film pressure is presented and its dynamic characteristics investigated numerically and experimentally. A numerical method based on a time-marching static model was applied to assess the orbit trajectory path of the rotor upon a perturbation. Experimental results were obtained to validate the effect of the self-generated squeeze-film pressure on the stability of the rotor. Analyzing the Fast Fourier Transform (FFT) responses of the rotor orbits enabled identification of self-excited whirling instabilities. Both numerical and experimental results showed that increasing the squeeze-film effect of the bearing could raise the threshold speed of instability
Sowing dates effect on Camelina growth in different EU climatic zones
No full textCamelina sativa (L.) Crantz, is an annual plant belonging to the Brassicaceae family, as rapeseed. It is native to central Europe where it was widely cultivated until the 1940s. However, only recently it gained the interest of the energy and bio-based industries as a low-cost non-food crop for aviation biofuel production and the oleochemical industry, due to its high oil content (up to 40%) and suitable oil profile. Field trials are performed at different locations in Europe, to study the effect of sowing dates on camelina seed and oil yields, in three different environments, the South (Greece) and North Mediterranean (Italy) climatic zones as well as the Continental zone (Poland). The activity was organized in two separate experiments: autumn sowing and spring sowing with two camelina varieties: Midas, a spring variety supplied by Linnaeus Plant Science (Canada), and Luna, a commercial winter variety from Poland. Total biomass ranged between 2.8 – 9.8 Mg DM ha-1, depending on the site and sowing seasons, with the highest figures in Italy and the lowest in Greece. Seed yields ranged from 0.56 – 2.11 Mg DM ha-1, depending on the site and sowing seasons, with the highest figures in the mild Mediterranean environments. Likewise, oil content ranged between 36.50 – 40.55%. Winter camelina reached almost double the seed yield compared to the spring crop for the same spring variety, Midas. Autumn sowing was found more productive than spring sowing for seed yields and oil content both in Greece and Italy, while in Poland, only real winter camelina varieties survive winter
Mediterranean corals through time: from Miocene to Present
No full textStony corals, especially scleractinians, are a recurrent component of the benthic fauna of the Mediterranean basin and its Mesozoic-to-Cenozoic precursors. Both morphological and geochemical features of coral skeletons place these organisms among the most important natural paleoarchives of the Mediterranean geological history. The present day low diversity
of the Mediterranean scleractinian fauna (25 genera and only 33 species) strikingly contrasts with its high diversity in the Early-Middle Miocene (over 80 genera and hundreds of species). The decline in coral richness has occurred since the late Middle Miocene onwards. This impoverishment trend was not linear, but abrupt in shallow-water environments during and immediately after the Late Miocene and more gradual since the Pliocene
onwards. At the end of the Miocene, the Mediterranean coral fauna underwent a drastic modification that led to the disappearance of almost all zooxanthellate corals and the wel lestablished shallow-water coral-reef province. However, the generic diversity of azooxanthellate and deep-water corals did not undergo signifi cant modifi cations, that were
instead much stronger at the end of the Pliocene and of the Pleistocene. Indeed, before the Calabrian stage, all remnant Indo-Pacifi c-like azooxanthellate genera disappeared and a clear NE Atlantic affi nity was established, whereas at the Pleistocene – Holocene boundary,
there was a clear reduction in psychrospheric deep-water taxa. The causes that led to the impoverishment of the Mediterranean coral fauna diversity are complex and not all fully understood. However, there is a clear link between the coral diversity decrease, the gradual northward shift outside the tropical belt of the Mediterranean region, and the major climate
modifications on a global scale during the last 20 million years
Investigation of Factors Related to Surface-Initiated Cracks in Flexible Pavements
No full textThis report works to identify potential mechanisms for the occurrence of top-down cracking, as well as to investigate stress patterns and concentrations due to surface load and preexisting transverse (thermal) cracks. It attempts to provide information on surface stresses that derives from both theory and experiments. In particular, contact mechanics solutions are analyzed to gain information on loads that are subsequently used in performing numerical evaluation of surface stresses. Examples of three-dimensional computations using the finite element code ABAQUS illustrate the analysis, and comparisons of stresses for uncracked and cracked pavements are made. The report concludes that the presence of a transverse crack in the AC layer significantly increases the vertical stresses in the base. It also has a noticeable effect on the horizontal stresses in the AC layer. Keywords-longitudianal cracks, transverse cracks, flexible pavements, ABAQUS finite element analysisLocal Road Research BoardHolewinski, Jill M.; Soon, Seechew; Drescher, Andrew; Stolarski, Henryk K.. (2003). Investigation of Factors Related to Surface-Initiated Cracks in Flexible Pavements. Retrieved from the University Digital Conservancy, https://hdl.handle.net/11299/895
A conformational analysis of the physical aging of Bisphenol-A Polycarbonate
No full textVita"Major subject: Chemistry
Carbon supported Ni-Mo catalysts prepared by spray drying for hydrodechlorination of polychlorinated biphenyls
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