744 research outputs found
A guided tour in the Lab
No full textJim Cassels, ?.., Francis Farley, Norman Ramsey are briefed by Gert Harigel. Albert Burger (left) and ?.. (right) on the backgroun
High-resolution recording of particle tracks with in-line holography in a large cryogenic bubble chamber
No full textHolography has been used successfully in combination with conventional optics for the first time in a large cryogenic bubble chamber, the 15-Foot Bubble Chamber at the Fermi National Accelerator Laboratory (FNAL), during a physics run in a high-energy neutrino beam. The innovative system combined the reference beam with the object beam, irradiating a conical volume of ~1.5 m/sup 3/. Bubble tracks from neutrino interactions with a width of ~120 mu m have been recorded with good contrast. The ratio of intensities of the object light to the reference light striking the film is called the beam branching ratio (BBR). We obtained in our experiment an exceedingly small minimum-observable ratio of BBR=(0.54/0.21)*10/sup -7/. The technology has the potential for a wide range of applications. This paper describes the various difficulties in achieving the success. It required the development of laser pulse stretching via enhanced closed loop control with slow Q-switching, to overcome excessive heating of the cryogenic liquid by the powerful laser beam. A sophisticated system of light-absorbing baffles had to be installed to avoid stray light reaching the holographic film. Optical decoupling of classical and holographic illumination systems was required. Real and virtual image replay machines for holograms were built, tailored to our illumination technique. (15 refs)
Unearthing the Real Process Behind the Event Data The Case for Increased Process Realism
No full textThis book is a revised version of the PhD dissertation written by the author at Hasselt University in Belgium.This dissertation introduces the concept of process realism. Process realism is approached from two perspectives in this dissertation. First, quality dimensions and measures for process discovery are analyzed on a large scale and compared with each other on the basis of empirical experiments. It is shown that there are important differences between the different quality measures in terms of feasibility, validity and sensitivity. Moreover, the role and meaning of the generalization dimension is unclear. Second, process realism is also tackled from a data point of view. By developing a transparent and extensible tool-set, a framework is offered to analyze process data from different perspectives. From both perspectives, recommendations are made for future research, and a call is made to give the process realism mindset a central place within process mining analyses.
In 2020, the PhD dissertation won the “BPM Dissertation Award”, granted to outstanding PhD theses in the field of Business Process Management
Authorship as cultural performance: new perspectives in authorship studies
No full textThis article proposes a performative model of authorship, based on the historical alternation between predominantly 'weak' and 'strong' author concepts and related practices of writing, publication and reading. Based on this model, we give a brief overview of the historical development of such author concepts in English literature from the Middle Ages to the twentieth century. We argue for a more holistic approach to authorship within a cultural topography, comprising social contexts, technological and media factors, and other cultural developments, such as the distinction between privacy and the public sphere
A resilience assessment framework for complex engineered systems using graphical evaluation and review technique (GERT)
No full textSystem resilience characterizes the capability of maintaining the required functionality under disruptions, which is of great significance in evaluating the productivity and safety of complex engineered systems. Although most studies conduct resilience assessment from qualitative and quantitative perspectives, system functionality that reflects functional requirements for complex engineered systems needs to be elaborated. In addition, given that complex engineered systems achieve dynamic performance during disruptions, measuring the actual performance under uncertainty is imperative. To this end, this paper develops a quantitative framework to assess the resilience of complex engineered systems. The developed framework comprises three phases, functionality analysis, performance evaluation, and resilience assessment. Firstly, system functionality is analyzed using a functional tree illustrating the relationship between functions. The overall objective, primary functions, and sub-functions are identified according to task requirements. Secondly, system performance is quantified considering uncertain factors through Graphical Evaluation and Review Technique (GERT). Probabilistic branches and network logic are employed to represent the implementation of various functions. Finally, resilience assessment is carried out from the perspectives of anticipation, absorption, adaptation, and restoration abilities. A case study on the satellite network shows the effectiveness of the developed framework. The developed framework determines system functionality based on task requirements, evaluates system performance with limited information, and accurately assesses system resilience.Safety and Security Scienc
Nucléation dans les chambres à bulles
No full textPlusieurs sources et mécanismes pour la création de bulles dans les liquides surchauffés sont discutés. Les chambres à bulles peuvent être remplies avec une grande variété de liquides, par exemple les liquides cryogéniques hydrogène, deutérium, néon, argon et azote, des mélanges néon/hydrogène et argon/azote, ou les liquides " chauds " propane et divers Fréons® comme le Fréon-13B1®. L'état surchauffé est généralement obtenu par un mouvement rapide d'un piston ou d'une membrane, mais il peut aussi être produit par des ondes ultrasoniques, de choc, ou en mettant les liquides sous tension. La formation des bulles peut être initiée par les particules
ionisantes, la lumière (laser) intense ou sur les surfaces rugueuses. La création de bulles embryonnaires n'est pas complètement connue, mais la croissance macroscopique et la condensation peuvent être calculées, permettant l'estimation de la charge de chaleur dynamique
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