1,720,988 research outputs found
Production, scaling and application of nanostructured metal multilayers as post-weld treatment
Full text linkCu/Ni Nanostructured Metal Multilayer coatings are introduced as a new post-weld
treatment method.
Steel specimen with a double V-groove butt-weld are coated with a Cu/Ni NMM
coating with an overall thickness of 9 μm, consisting of a 1 μm Ni base layer, a
nanolaminate structure with a bilayer thickness of 50 nm and Cu and Ni single layer
thicknesses of 15 nm and 35 nm respectively. The coating is electroplated onto the
steel substrate with a single bath method.
The coated steel specimens are tested in tension-tension fatigue and the corresponding
S-N curves are calculated from the fatigue results.
SEM, TEM and EDX investigations provide insights into the material characterization
of the nanolaminate structure and the understanding of NMM failure mechanisms.Cu/Ni Nanostrukturierte Metall Multilayer werden als neue Schweißnahtnachbehandlungsmethode
vorgestellt.
Stahlproben mit einer geschweißten Doppel-V-Stumpfnaht werden mit Cu/Ni 9 μm
dicken NMM beschichtet, die aus einer 1 μm Ni Grundbeschichtung, einer Doppelschichtdicke
von 50 nm und Cu/Ni Einzelschichtdicken von 15 nm und 35 nm
bestehen. Die Beschichtung wird galvanisch mit einem Einzelbadverfahren auf die
Stahlgrundlage aufgebracht.
Die beschichteten Stahlproben werden im Zugschwellbereich auf Ermüdung getestet
und die dazugehörigen Wöhlerkurven werden aus den Ermüdungsergebnissen berechnet.
REM, TEM und EDX Untersuchungen geben Einblicke in die Materialcharakterisierung
der Nanolaminatstrukturen und dem Verständnis von NMM Versagensmechanismen
Physical explanation for vibro-acoustic modulation in a structure due to local and global nonlinearities
No full textThis dissertation suggests a physical explanation revealing why any elastic nonlinearity may cause vibro-acoustic modulation (VAM) in a dynamic system that is excited by two waves simultaneously (Xω and XΩ) in case the corresponding frequencies differ significantly (ω >> Ω): The low frequency (LF) vibration XΩ activates the nonlinearity and varies quasi-statically the system’s natural frequency ω0 corresponding to the dominant mode shape. The amplitude and phase of the ultrasonic system response depend on the natural frequency ω0 and are therefore modulated with low frequency Ω. This analytical explanation is built upon the assumption that the system reaches a steady-state vibration (constant amplitude and phase over time) due to ultrasonic excitation Xω before the LF vibration XΩ can change the dy- namic properties of the system significantly. The fulfillment of this assumption is validated experimentally and numerically for an aluminum plate-like structure and excitation frequencies Ω = 10Hz · 2π and 180kHz · 2π < ω < 230kHz · 2π: It is shown that the minimum and maximum amplitudes in the modulated ultrasonic system response match the respective steady-state amplitudes under static loading with a negligible error that is <1%. The beauty of the explanation is that it does not only work for the local nonlinear-elastic behavior of a defect, but also for any non-damage-induced (local or global) nonlinearity in the system which may cause modulation as well. The explanation is employed to conclude and demonstrate the following five analytical findings: 1) Any elastic nonlinearity may cause amplitude modulation and phase modulation at the same time. 2) The nonlinearity can cause envelope functions in the modulated system response with a variety of different characteristic shapes. 3) The maximum amplitude in the modulated system response in time domain can either coincide with the minimum or the maximum stress state corresponding to the LF vibration XΩ. 4) Different nonlinearities in the same system can cause contrary modulations that neutralize each other. 5) The steady-state evaluation of the ultrasonic system response allows—theoretically—VAM applications without exciting the LF vibration XΩ. Finally, three nonlinearities in the same system are investigated separately: Two non-damage-induced nonlinearities (the variation of geometric stiffness and the nonlinear-elastic material behavior of aluminum) and one damage-induced nonlinearity (the contact of fatigue crack surfaces) are considered. Numerical simulations are carried out to quantify and compare the modulation they cause individually in the system response. The results comply with the analytical findings concluded from the physical explanation and emphasize that the conventional VAM evaluation for damage monitoring is error prone.Diese Dissertation stellt eine analytische physikalische Erklärung für das Auftreten Vibro-
Akustischer Modulation in einer Struktur aufgrund einer elastischen Nichtlinearität vor. Es
werden u.a. die folgenden Erkenntnisse daraus abgeleitet und experimentell sowie numerisch
demonstriert: Eine elastische Nichtlinearität kann eine Reihe charakteristischer Einhüllender in
der Systemantwort hervorrufen. Unterschiedliche Nichtlinearitäten in dem selben dynamischen
System können gegenläufige Modulationen in der Systemantwort hervorrufen, die sich
neutralisieren. Die statische Auswertung der Systemantwort ermöglicht VAM-Anwendungen,
ohne die niedrigfrequente Vibration in der Struktur anzuregen
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
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