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Search Results: 1 - 10 of 84682 matches for " W. Herr "
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Proceedings of the ICFA Mini-Workshop on Beam-Beam Effects in Hadron Colliders (BB2013), CERN, Geneva, Switzerland, 18 - 22 Mar 2013
W. Herr,G. Papotti
Physics , 2014, DOI: 10.5170/CERN-2014-004
Abstract: This report contains the Proceedings of the ICFA Mini-Workshop on Beam-Beam Effects in Hadron Colliders held at CERN from 18 to 22 March 2013. It was the first of its kind after the successful start of LHC operation where a vast amount of beam-beam observations emerged. It brought together 58 international experts in the field and the purpose of this workshop was to review the present knowledge in the fields of beam-beam theory, simulations and observations. In the summary session the participants acknowledged the enormous progress made in recent years and the introduction of new concepts and tools. The workshop was concluded by a discussion on future research work with emphasis on the LHC operation and future circular colliders.
Analysis of long-range studies in the lhc - Comparison with the model
D. Kaltchev,W. Herr
Physics , 2014, DOI: 10.5170/CERN-2014-004.93
Abstract: We find that the observed dependencies (scaling) of long-range beam-beam effects on the beam separation and intensity are consistent with the simple assumption that, all other parameters being the same, the quantity preserved during different set-ups is the first-order smear as a function of amplitude.
Operational considerations on the stability of colliding beams
X. Buffat,W. Herr,T. Pieloni
Physics , 2014, DOI: 10.5170/CERN-2014-004.193
Abstract: While well studied in the absence of beam-beam and while colliding head-on, the stability of the LHC beams can be very critical in intermediate steps. During the squeeze, the long-range beam-beam interaction becomes a critical component of the beam's dynamics. Also, while the transverse separation at the interaction points is collapsed, the beam-beam forces change drastically, possibly deteriorating the beam's stability. Finally, during luminosity production, the configuration of the LHC in 2012 included few bunches without head-on collision in any of the interaction points having different stability properties. Stability diagrams are being evaluated numerically in these configurations in an attempt to explain instabilities observed in these phases during the 2012 proton run of the LHC.
Stability diagram of colliding beams
X. Buffat,W. Herr,N. Mounet,T. Pieloni
Physics , 2014, DOI: 10.5170/CERN-2014-004.57
Abstract: The effect of the beam-beam interactions on the stability of impedance mode is discussed. The detuning is evaluated by the means of single particle tracking in arbitrarily complex collision configurations, including lattice non-linearities, and used to numerically evaluate the dispersion integral. This approach also allows the effect of non-Gaussian distributions to be considered. Distributions modified by the action of external noise are discussed.
Observations of beam-beam effects at the LHC
G. Papotti,X. Buffat,W. Herr,R. Giachino,T. Pieloni
Physics , 2014,
Abstract: This paper introduces a list of observations related to the beam-beam interaction that were collected over the first years of LHC proton physics operation (2010-12). Beam-beam related effects not only have been extensively observed and recorded, but have also shaped the operation of the LHC for high-intensity proton running in a number of ways: the construction of the filling scheme, the choice of luminosity levelling techniques, measures to mitigate instabilities, and the choice of settings for improving performance (e.g. to reduce losses), among others.
Statistics for Categorical Surveys—A New Strategy for Multivariate Classification and Determining Variable Importance
Alexander Herr
Sustainability , 2010, DOI: 10.3390/su2020533
Abstract: Surveys can be a rich source of information. However, the extraction of underlying variables from the analysis of mixed categoric and numeric survey data is fraught with complications when using grouping techniques such as clustering or ordination. Here I present a new strategy to deal with classification of households into clusters, and identification of cluster membership for new households. The strategy relies on probabilistic methods for identifying variables underlying the clusters. It incorporates existing methods that (i) help determine the optimal cluster number, (ii) directly identify variables underlying clusters, and (iii) identify the variables important for classifying new cases into existing clusters. The strategy uses the R statistical software, which is freely accessible to anyone.
Exoskeletons and orthoses: classification, design challenges and future directions
Hugh Herr
Journal of NeuroEngineering and Rehabilitation , 2009, DOI: 10.1186/1743-0003-6-21
Abstract: The current series of the Journal of NeuroEngineering and Rehabilitation (JNER) is dedicated to recent advances in robotic exoskeletons and powered orthoses. The articles in this special issue cover a broad spectrum of embodiments, from orthotic devices to assist individuals suffering from limb pathology to limb exoskeletons designed to augment normal, intact limb function.To set the stage for this special issue, I classify exoskeletons and orthoses into four categories and provide design examples within each of these. I discuss devices that act in series with a human limb to increase limb length and displacement, and devices that act in parallel with a human limb to increase human locomotory economy, augment joint strength, and increase endurance or strength. For each exoskeletal type, I provide a design overview of hardware, actuation, sensory, and control systems for a few characteristic devices that have been described in the literature, and when available, describe the results of any quantitative evaluation of the effectiveness of the devices in performing their intended tasks. Finally, I end with a discussion of the major design challenges that have yet to be overcome, and possible future directions that may provide resolutions to these design difficulties.For the purposes of this commentary, exoskeletons and orthoses are defined as mechanical devices that are essentially anthropomorphic in nature, are 'worn' by an operator and fit closely to the body, and work in concert with the operator's movements. In general, the term 'exoskeleton' is used to describe a device that augments the performance of an able-bodied wearer, whereas the term 'orthosis' is typically used to describe a device that is used to assist a person with a limb pathology.It is perhaps worth noting that the term "exoskeleton" has come to describe systems that are comprised of more than just a passive protective and supporting shell, as its usage in biology would suggest. "Exoskeleton" within o
VD 16, 17 und 18: Retrospektive nationalbibliographische Verzeichnung vor dem Hintergrund sich ver ndernder technischer Rahmenbedingungen
Wiebke Herr
Perspektive Bibliothek , 2012, DOI: 10.11588/pb.2012.2.9459
Abstract: Beim VD 16, 17 und 18 handelt es sich um drei retrospektive Nationalbibliographien des 16., 17. und 18. Jahrhunderts. Angelegt wurden die drei Verzeichnisse der im deutschen Sprachraum/Sprachbereich erschienenen Drucke zeitlich versetzt zueinander. Die gesamte Entstehungsspanne reicht dabei mittlerweile über 50 Jahre. Dass es im Laufe der Zeit zu methodischen Verschiebungen gekommen ist, erstaunt deshalb wenig. Dieser Artikel konzentriert sich gezielt auf Ver nderungen, die sich durch technische Entwicklungen für den Charakter der VDs ergeben haben. Als wesentliche technische Einflussgr en lassen sich Verzeichnisformate und Digitalisierungsm glichkeiten beschreiben. Folgen und Chancen ergeben sich daraus vor allem für vier Bereiche: Funktionen, Erschlie ungsstandards und Vollst ndigkeit der VDs sowie die Zugriffsm glichkeiten auf ihre Daten.
Exlibris als Provenienzmerkmale und eigenst ndige Druckgraphik: Sammlungen, Erschlie ungsstand, Nutzungspotential
Wiebke Herr
Perspektive Bibliothek , 2012, DOI: 10.11588/pb.2012.1.9400
Abstract: Dem Themenfeld Exlibris n hert sich dieser Aufsatz von zwei Seiten. In einem ersten Teil soll das Exlibris in seinen wichtigsten Wesensmerkmalen beschrieben werden. Eingegangen wird dabei auf den Begriff Exlibris“ und m gliche Alternativen. Die Frage nach sinnvollen Begrifflichkeiten h ngt wiederum eng mit der Frage nach den Funktionen eines Exlibris zusammen. Es folgt deshalb die Vorstellung typischer Bildmotive, der wichtigsten Drucktechniken und Gestaltungsstile von Exlibris. Ein zweiter Teil des Aufsatzes besch ftigt sich dann mit einer Art Au ensicht auf den Gegenstand Exlibris. Zum einen geht es darum, zusammenzufassen, welche Forschungsinteressen sich mit einem Exlibris verbinden lassen. Zum anderen wird eine Auswahl an Katalogen und Datenbanken vorgestellt, die Exlibris verzeichnen. Die Klammerfrage wird dabei sein, in wie fern die zur Verfügung stehenden Rechercheinstrumente eigentlich den wissenschaftlichen Interessen gerecht werden.
Give Me My Father's Body: The Life of Minik the New York Eskimo, by Kenn Harper, Steerforth Press, South Royalton, VT, 2000
Melody Herr
Bulletin of the History of Archaeology , 2001, DOI: 10.5334/bha.11104
Abstract: When Arctic explorer Robert Peary came home in September 1897, he brought with him a thirty-ton meteorite, an ethnological collection, and a group of Polar Eskimos for the American Museum of Natural History, which were immediately put on display. No matter that four of the six Eskimos died: the Museum just removed them from temporary exhibits and catalogued in them permanent collections. Of the two surviving, one returned to Greenland the following summer, the other remained in the household of a Museum administrator, William Wallace. This little orphan named Minik became the "New York Eskimo" of the title, and the phrase aptly summarizes his oxymoronic life.
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