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Wyszukujesz frazę "Hofmann, R." wg kryterium: Autor


Wyświetlanie 1-10 z 10
Tytuł:
Constraints on the Lamina Density of Laminar Bone Architecture of Large-Bodied Dinosaurs and Mammals
Autorzy:
Hofmann, R.
Stein, K.
Sender, P.M.
Powiązania:
https://bibliotekanauki.pl/articles/946035.pdf
Data publikacji:
2014
Wydawca:
Polska Akademia Nauk. Instytut Paleobiologii PAN
Tematy:
dinosauria
mammalia
bone histology
laminar bone
lamina thickness
lamina density
Opis:
Laminar bone tissue is commonly found in Dinosauria (including birds) and Mammalia. The tissue emerged convergently several times, and its frequent occurrence among amniotes has stimulated researchers to study some of its geometric features. One such feature is lamina thickness or lamina density (LD, expressed as number of laminae per mm). We measured LD in a sample of sauropodomorph dinosaur taxa (basal sauropodomorphs, basal sauropods and Neosauropoda) and compared it with LD of a selection of mammals. LD is relatively constrained within the groups; nonetheless mean sauropodomorph LD differs significantly from mean mammal LD. However, increasing sample size with other dinosaur groups and more perissodactyls and artiodactyls may alter this result. Among sauropods, LD does not change drastically with increasing femur length although a slight tendency to decrease may be perceived. We conclude that the laminar vascular architecture is most likely determined by a combination of structural and functional as well as vascular supply and physiological causes.
Źródło:
Acta Palaeontologica Polonica; 2014, 59, 2; 287-294
0567-7920
Pojawia się w:
Acta Palaeontologica Polonica
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Palaeoecology of the Spathian Virgin Formation (Utah, USA) and its implications for the Early Triassic recovery
Autorzy:
Hofmann, R.
Hautmann, M.
Wasmer, M.
Bucher, H.
Powiązania:
https://bibliotekanauki.pl/articles/21319.pdf
Data publikacji:
2013
Wydawca:
Polska Akademia Nauk. Instytut Paleobiologii PAN
Tematy:
paleoecology
Spathian Virgin Formation
Utah
USA
Early Triassic
Triassic
recovery
diversity
biotic recovery
mass extinction
Opis:
The Spathian (late Early Triassic) Virgin Formation of south−western Utah (USA) yields a comparatively diverse benthic fauna that flourished ~2 Ma after the end−Permian mass extinction. In this study, we present quantitative palaeoecological data, which are analysed in the context of depositional environments. This integrated approach helps to discriminate between effects of the end−Permian mass extinction event and local environmental factors on alpha diversity and ecological structure of the Virgin Fauna. Shallow subtidal environments yield the highest species richness and lowest dominance val− ues as recorded in two benthic associations, the Eumorphotis ericiusAssociation and the Protogusarella smithi Association, both ofwhich contain 20 benthic species (bivalves, gastropods, brachiopods, echinoderms, and porifers). Tidal inlet deposits yield a low diverse fauna (Piarorhynchella triassica Association) with a very high dominance of filter feeders adapted to high energy conditions.Another comparably low diverse fauna is recorded by the Bakevellia exporrecta Association, which occurs in deposits of the offshore transition zone,most likely reflecting unconsolidated substrates. A single sample contain− ing five bivalve species (Bakevellia costata Assemblage) is recorded from a marginal−marine setting. The Virgin fauna yields a bulk diversity of 30 benthic species (22 genera) of body fossils and 14 ichnogenera and, thus, represents the most di− verse marine bottom fauna known so far from the Early Triassic. Our results suggest that oceanographic conditions during the early Spathian enabled ecosystems to rediversify without major abiotic limitations. However, taxonomical differentia− tion between habitats was still low, indicating a time lag between increasing within−habitat diversity (alpha diversity) and the onset of taxonomical differentiation between habitats (beta diversity). We suggest that taxonomical habitat differentia− tion after mass extinction events starts only when within−habitat competition exceeds a certain threshold, which was not yet reached in the Spathian of the investigated area. This interpretation is an alternative to previous suggestions that the preva− lence of generalistic taxa in the aftermath of mass extinction events reflects protracted environmental stress. The onset of in− creasing beta diversity is a potential criterion for distinguishing two major recovery phases, the first ending with habitat satu− ration and the second ending with the completion of ecosystem differentiation.
Źródło:
Acta Palaeontologica Polonica; 2013, 58, 1
0567-7920
Pojawia się w:
Acta Palaeontologica Polonica
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Non-invasive parameter identification by using the least squares method
Nieinwazyjna identyfikacja parametrów przy wykorzystaniu metody najmniejszych kwadratów
Autorzy:
Neugebauer, R.
Hellmich, A.
Hofmann, S.
Schlegel, H.
Powiązania:
https://bibliotekanauki.pl/articles/140192.pdf
Data publikacji:
2011
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:
identyfikacja parametrów
metoda najmniejszych kwadratów
urządzenia kontrolujące pracę serwonapędów
parameters identification
least squares method
motion control
Opis:
The paper presents an adapted least squares identification method for reduced-order parametric models. On the example of the open velocity loop, different model approaches were implemented in a motion control system. Furthermore, it is demonstrated how the accuracy of the method can be improved. Finally, experimental results are shown.
W artykule przedstawiono metodę identyfikacji, wykorzystującą metodę najmniejszych kwadratów, przystosowaną do modeli parametrycznych ograniczonego rzędu. Na przykładzie otwartej pętli regulacji prędkości zilustrowano różne podejścia do modelowania systemów sterowania. Zademonstrowano ponadto, jak można poprawić dokładność metody. W końcowej części pracy przedstawiono wyniki doświadczalne.
Źródło:
Archive of Mechanical Engineering; 2011, LVIII, 2; 185-194
0004-0738
Pojawia się w:
Archive of Mechanical Engineering
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Time-based method for the combined identification of velocity-loop parameters
Metoda złożonej identyfikacji parametrów pętli sterowania prędkością wykorzystującą właściwości czasowe
Autorzy:
Neugebauer, R.
Hofmann, S.
Hellmich, A.
Schlegel, H.
Powiązania:
https://bibliotekanauki.pl/articles/140194.pdf
Data publikacji:
2011
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:
identyfikacja parametrów
model parametryczny
urządzenia kontrolujące pracę serwonapędów
parameters identification
parametric model
motion control
Opis:
Today, a cascaded system of position loop, velocity loop and current loop is standard in industrial motion controllers. The exact knowledge of significant parameters in the loops is the basis for the tuning of the servo controllers. A new method to support the commissioning has been developed. It enables the user to identify the moment of inertia as well as the time constant of the closed current loop simultaneously. The method is based on the auto relay feedback experiment by Aström and Hägglund. The model parameters are automatically adjusted according to the time behaviour of the controlled system. For this purpose, the auto relay feedback experiment is combined with the technique of gradual pole compensation. In comparison to other existing methods, this approach has the advantage that a parametric model for the open velocity loop is derived directly.
We współczesnych przemysłowych układach sterowania ruchem standardowo wykorzystuje się kaskadowe systemy z pętlą sterowania położeniem, prędkością i pętlą prądową. Dokładna znajomość istotnych parametrów pętli jest podstawą dla optymalizacji działania serworegulatorów. Autorzy opracowali nową metodę wspomagającą pozyskiwanie tych danych. Umożliwia ona jednoczesną identyfikację momentu bezwładności i stałej czasu w zamkniętej pętli prądowej. Metoda jest oparta na eksperymencie Aströma i Hägglunda z automatycznym przekaźnikowym sprzężeniem zwrotnym. Parametry modelu są dobierane automatycznie, biorąc pod uwagę właściwości sterowanego systemu w dziedzinie czasu. Wykorzystano w tym celu eksperyment z automatycznym przekaźnikowym sprzężeniem zwrotnym w połączeniu z techniką stopniowej kompensacji biegunów. W porównaniu do innych istniejących metod, zaletą takiego podejścia jest możliwość bezpośredniego wyznaczenia modelu parametrycznego dla otwartej pętli sterowania prędkością.
Źródło:
Archive of Mechanical Engineering; 2011, LVIII, 2; 175-184
0004-0738
Pojawia się w:
Archive of Mechanical Engineering
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Non - invasive identification of servo drive parameters
Autorzy:
Neugebauer, R.
Hellmich, A.
Hofmann, S.
Schlegel, H.
Powiązania:
https://bibliotekanauki.pl/articles/384413.pdf
Data publikacji:
2012
Wydawca:
Sieć Badawcza Łukasiewicz - Przemysłowy Instytut Automatyki i Pomiarów
Tematy:
identification
parametric model
natural excitation
least squares method
SIMOTION
Opis:
For the tuning of servo controllers as well as for monitoring functions, significant parameters of the controlled system are required. In contrast to identification methods with determined input signals, the paper focuses on the problem of identification with regular process movements (non-invasive identification), leading to a lack of power density in some frequency ranges. A nonlinear Least Squares (LS) approach with single mass system and friction characteristic is investigated regarding the accomplishable accuracy and necessary constraints. The proposed method is applicable on industrial motion controllers and has been carried out with a multitude of input sequences. To verify the performance of the approach, achieved experimental results for the model parameters are exposed.
Źródło:
Journal of Automation Mobile Robotics and Intelligent Systems; 2012, 6, 2; 13-16
1897-8649
2080-2145
Pojawia się w:
Journal of Automation Mobile Robotics and Intelligent Systems
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Photoconductivity Study of Sputter-Deposited $Cu_2O$ Films
Autorzy:
Bhattacharyya, S.
Reppin, D.
Sanguino, P.
Ayouchi, R.
Polity, A.
Schwarz, R.
Hofmann, D.
Meyer, B.
Powiązania:
https://bibliotekanauki.pl/articles/1492344.pdf
Data publikacji:
2011-12
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
78.66.-w
73.50.-h
73.61.-r
Opis:
Cuprous oxide $(Cu_2O)$ thin films were deposited by radio frequency sputtering technique on fused silica substrates. The X-ray diffraction study of the $Cu_2O$ samples showed reflections from (111) and (200) planes of cubic $Cu_2O$. The samples were then annealed at 1008 K in nitrogen $(N_2)$ atmosphere. Annealed samples indicated strain relaxation. The samples were then characterized optically by measuring the transmittance using an ultraviolet-visible-near infrared photospectrometer. The band gap of the as-deposited samples were found to be ≈ 2.1 eV, whereas the annealed samples had a band gap of ≈ 2.6 eV. The transient photocurrent decay measurements of the annealed films indicated slow non-exponential power law decays in several time windows, indicating multiple trapping of the carriers in the deep defects within the band gap. The steady-state photo and dark current measurement and persistent photocurrent (PPC) was carried out on the annealed samples. In general, the photocurrent was found to be much smaller than the dark current. The steady-state and transient photocurrent measurements were utilized to determine the carrier lifetime-mobility product, 〈μτ 〉 of the samples and to determine the carrier mobility, 〈μ 〉.
Źródło:
Acta Physica Polonica A; 2011, 120, 6A; A-011-A-014
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Numerical methods in underwater acoustics - sound propagation and backscattering
Autorzy:
Nolte, B.
Ehrlich, J.
Hofmann, H.-G.
Schäfer, I.
Schäfke, A.
Stoltenberg, A.
Burgschweiger, R.
Powiązania:
https://bibliotekanauki.pl/articles/331712.pdf
Data publikacji:
2015
Wydawca:
Polskie Towarzystwo Akustyczne
Tematy:
stochastic ray tracing
German Navy
Opis:
This report summarizes an overview given at the XXXII Symposium on Hydroacoustics (SHA 2015) over several modelling techniques that are used in the context of military applications at the Research Department FWG of the German Bundeswehr Technical Centre for Ships and Naval Weapons, Maritime Technology and Research (WTD 71). For the modelling and understanding of sound propagation a physical model consisting of a tank for scaled measurements and the corresponding numerical simulation is presented. The basic formalism of stochastic ray tracing of the German Navy sonar simulation MOCASSIN is explained and compared to traditional deterministic ray tracing including the comparison with measurements. Strategies for the approximate calculation of the sonar target strength of large underwater objects with the use of boundary element methods, fast multipole methods and a ray-based algorithm are presented and the results of the calculations of several test objects are shown.
Źródło:
Hydroacoustics; 2015, 18; 127-140
1642-1817
Pojawia się w:
Hydroacoustics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
In Situ Neutron Diffraction Characterization of Phases in Co-Re-Based Alloys at High Temperatures
Autorzy:
Strunz, P.
Mukherji, D.
Gilles, R.
Gasser, U.
Beran, P.
Farkas, G.
Hofmann, M.
Karge, L.
Rösler, J.
Powiązania:
https://bibliotekanauki.pl/articles/1402124.pdf
Data publikacji:
2015-10
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
61.05.fg
61.66.Dk
Opis:
Co-Re-based alloys strengthened by carbides are promising candidates for new high-temperature alloys for gas turbine applications. The high temperature microstructure and its stability are of utmost importance, e.g. due to strengthening-phase selection. Neutron scattering, providing in situ information at high temperatures, was extensively used in the past for the Co-Re alloys research. The paper focuses on TaC strengthened alloy, particularly on the stability TaC precipitates which were previously shown not to dissolve up to at least 1300°C. Small-angle neutron scattering shows that its finer morphological variant - most suitable for high temperature strengthening - coarsened even at relatively low temperature of 1000°C. This coarsening is faster at higher temperatures and the mean size exceeded 1000 Å (i.e. the size - detection limit of the used facility) after 4 h hold at 1200°C.
Źródło:
Acta Physica Polonica A; 2015, 128, 4; 684-688
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Compensation Models in Chlorine Doped CdTe Based on Positron Annihilation and Photoluminescence Spectroscopy
Autorzy:
Stadler, W.
Hofmann, D. M.
Meyer, B. K.
Krause-Rehberg, R.
Polity, A.
Abgarjan, Th.
Salk, M.
Benz, K. W.
Azoulay, M.
Powiązania:
https://bibliotekanauki.pl/articles/1934007.pdf
Data publikacji:
1995-11
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
71.55.Gs
78.70.Bj
78.55.Et
Opis:
In this investigation positron annihilation, photoluminescence and electron paramagnetic resonance techniques are employed to gain insight in the compensation of CdTe doped with the halogen Cl. We will demonstrate that the high resistivity of CdTe:Cl cannot be explained by the interaction between the shallow effective mass type donor Cl on Te site and the doping induced shallow acceptor complex, a Cd vacancy paired off with a nearest-neighbour Cl atom (A centre). From electron paramagnetic resonance investigations we conclude that the mid gap trap, often detected by electrical methods in CdTe, is not the isolated Cd vacancy.
Źródło:
Acta Physica Polonica A; 1995, 88, 5; 921-924
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Plasmon Enhancement of Fluorescence in Single Light-Harvesting Complexes from em Amphidinium carterae
Autorzy:
Bujak, Ł.
Piątkowski, D.
Mackowski, S.
Wörmke, S.
Jung, C.
Bräuchle, C.
Agarwal, A.
Kotov, N.
Schulte, T.
Hofmann, E.
Brotosudarmo, T.
Scheer, H.
Govorov, A.
Hiller, R.
Powiązania:
https://bibliotekanauki.pl/articles/1807594.pdf
Data publikacji:
2009-12
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
87.80.Nj
87.14.E-
87.64.M-
Opis:
We show that single peridinin-chlorophyll a-protein light-harvesting complexes from dinoflagellate Amphidinium carterae placed near to silver nanoparticles show strongly enhanced fluorescence emission. Single molecule spectroscopy experiments performed at room temperature point toward an enhancement of more than an order of magnitude for optimal conditions. Irrespective of the enhancement, we observe no effect of the metal nanoparticle on the fluorescence emission energy of the complex. This result provides a way to control the optical properties of biomolecules via plasmon excitations in metal nanoparticles.
Źródło:
Acta Physica Polonica A; 2009, 116, S; S-22-S-25
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
    Wyświetlanie 1-10 z 10

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